By David Lash

In February 1945, General Douglas MacArthur was poised to begin one of the great battles of his career. In front of him was Manila—capital of the Philippines, principal city of the island of Luzon, and, since the previous month’s invasion of the island at Lingayen Gulf, the chief goal of the Sixth Army. For nearly a month, he had poked, prodded, and pushed his methodical subordinates to drive toward the capital as rapidly as possible.

MacArthur’s opposite number, General Tomoyuki Yamashita, was willing to let MacArthur have his prize. There was not enough food for the local population, the buildings were flammable, and the surrounding flat terrain made it difficult to defend—especially since the battle for the island of Leyte. That effort, which he had strongly advised against, had cost him tens of thousands of his best troops along with the prospect of air and naval support for the defense of Luzon. So, Yamashita had ensconced his men firmly into mountain redoubts guarding strategic locations on Luzon, thereby forcing the Americans to come to him. If he could not stop them from taking the island, he could at least make them pay for it. At best, a spirited enough defense might make the United States think twice about invading the Japanese homeland. At the very least, it would reduce the number of Americans available for that invasion. Unfortunately, naval leaders in Manila ignored Yamashita and refused to surrender—a decision that would lead to one of the most horrific and tragic battles of the war. MacArthur knew that he would have to secure more than the city itself. It was imperative to seize its sources of water, which lay in the Sierra Madre mountains to the east. His men had taken the Novaliches Reservoir, 10 miles northeast of Manila, on February 5. But this was fed via aqueduct from Ipo (“EE-po”) Dam, which straddled the Angat River a further 15 miles northeast. Ten miles south of this was Wawa Dam, near the village of Montalban. With these dams in the hands of the Japanese, the situation would be precarious; the reservoir could not suffice for long without water from the mountains.

Taking the dams would not be easy. When General Yamashita had retreated to Baguio in northeastern Luzon, he had organized his forces into three primary groups. The Shobu Group, which he commanded himself, was the largest, consisting of 152,000 troops in the mountains north and east of Lingayen Gulf, where he could block the passes to the fertile Cagayan Valley, a source of food for his troops. A second command, the 30,000-man Kembu Group, was assigned to the Clark Field/Fort Stotsenburg complex and the surrounding Zambales Mountains/ Subic Bay area. And then there was the Shimbu (martial spirit) Group, consisting of 80,000 men scattered throughout southern Luzon at Manila, Laguna de Bay, the Bicol Peninsula, and the Ipo and Wawa Dams.

The core of Shimbu Group ended up in this latter area after its commander, Lt. Gen. Shizuo Yokoyama, withdrew what forces he could from Manila. His troops were a mixed lot, having been hastily assembled from various areas and units, but formed a nucleus around the 8th and 105th Divisions, which had moved north from Batangas and the Bicol Peninsula.

The westernmost defenses of the 30-mile front began in high terrain two miles north of Ipo Dam, extended south-southeast to Mount Oro, and then to Mount Pacawagan near Wawa Dam, and continued to a point west of Antipolo. From there, the defenses turned southeast to the Morong River Valley and ultimately to Laguna de Bay. The 9,000-man Kawashima Force was in the north, protecting Ipo Dam; the 12,000-man Kobayashi Force was in the central sector near Montalban and Wawa Dam; and the 9,000-man Noguchi Force held the south, concentrating near Antipolo and extending south to Pililla on Laguna de Bay. Five thousand of Yokoyama’s best troops were in reserve near the center of the line.

The Shimbu Group was well supplied, except for the Noguchi Force, much of which had been hurriedly withdrawn from the Bicol Peninsula. For food, Yokoyama would rely on the agricultural areas in the Bosoboso Valley and near Laguna de Bey and Lamon Bay. However, intensive agriculture had ceased in these areas early in the Japanese occupation, so any loss of their meager output would be disastrous.

An American soldier of the 43rd Infantry Division unleashes a deadly stream from his flamethrower during efforts to silence a Japanese pillbox.
An American soldier of the 43rd Infantry Division unleashes a deadly stream from his flamethrower during efforts to silence a Japanese pillbox.

Facing the Shimbu Group was the U.S. XIV Corps, headed by Lt. Gen. Oscar Griswold. The XIV Corps had been one of the U.S. Sixth Army’s three prongs in the Luzon invasion. At Lingayen Gulf, while I Corps fought advance elements of the Shobu group on the left, XIV Corps advanced down the Central Plain toward Manila, taking a detour to seize Clark Air Field and battle the remainder of the Kembu Group. It was replaced in that campaign by XI Corps, which had landed at Subic Bay and advanced eastward along the top of the Bataan Peninsula.

Now, while XIV Corps was beginning a devastating battle in Manila, Griswold had to start planning an offensive against the Shimbu Group’s mountain defenses. With insufficient manpower to attack the entire line at once, he would target the southern end first—the Noguchi and Kobayashi forces. Not only was Wawa Dam closer than Ipo Dam, but these forces, some of which were less than 15 miles from Manila, had artillery that was much too close for comfort. Furthermore, a southern campaign would cut off these groups from any reinforcements that might try to come up from farther south.

This was just what Yokoyama expected, so he had most of his reserves stationed in the Bosoboso Valley to meet this threat. This would have been a surprise to the Sixth Army commander, General Walter Krueger, who thought that the rough terrain and poor roads prevented the enemy from keeping a centrally located reserve that could support either or both of the southern and the northern positions. This was true enough for Ipo Dam, which was connected to Wawa Dam by only a narrow trail, but not true for the southern forces, which could be supplied via a new road. Furthermore, U.S. intelligence underestimated the size of the enemy. It was believed that only 12,000 to 13,000 troops were in the southern area, and 6,000 to 7,000 near Ipo Dam—in other words, about 20,000 troops instead of the actual 35,000 in this area.

Perhaps it was just as well for Krueger’s peace of mind that he did not know this, for he was about to begin the campaign with a severe manpower shortage. MacArthur may have wanted the dams, but they were not at the top of his priority list. He also wanted to open a shorter sea route from Leyte, seize and develop ports all along the coast of Luzon, and begin operations in the central and southern Philippines. This last item was a detour that had been given no prior authorization by Washington, but that did not stop MacArthur.

Against this ambitious agenda, fighting the Shimbu Line in formidable terrain portended tying up scarce resources in a long campaign. It would be better to contain and reduce the enemy forces there, he wrote Krueger. So, on February 7, only two days after the orders had gone out to seize the dams, MacArthur diverted the Luzon-bound 41st Infantry Division to the southern Philippines. He then started plucking other battalions and regiments from Krueger’s quiver, including the entire 40th Infantry Division. When it was all over, Krueger found that, instead of having 11 divisions and four regimental combat teams (RCTs), he had lost the equivalent of three divisions, and temporarily the 37th, which was being assigned to garrison duties in Manila.

Reluctantly, Krueger took the 6th Infantry Division (less the 1st RCT) from I Corps, knowing that this would weaken the campaign against the Shobu Group to the north, and gave it to Griswold’s XIV Corps.

The Japanese Had Stocked There Positions with a Wide Variety of Weapons, from Rifles, Mortars, Machine Guns, and Grenades to Antiaircraft Artillery, Antitank Guns, 105mm Howitzers, and 155mm Guns

Griswold decided to charge the 6th with the task of capturing both dams. But, in accordance with the “south first” strategy, he would use the 112th RCT (attached to the 6th) to keep an eye on the Ipo Dam sector, while an advance against Wawa Dam and the southern Shimbu Line would jump off on a 13-mile front along the Marikina River and proceed east. Beginning from a point near Montalban, where the river, running west from Wawa Dam, turned south, the 6th would advance in the direction of the dam. On its right, the 2nd Cavalry Brigade, 1st Cavalry Division would seize Antipolo and create a line that stretched southwest to Tagig, thereby securing the confluence of the Marikina and Pasig Rivers near the shore of Laguna de Bey.

American forces landing at Lingayen Gulf and on the western coast of Luzon confronted battle-hardened Japanese troops under General Tomoyuki Yamashita in the mountains outside Manila.
American forces landing at Lingayen Gulf and on the western coast of Luzon confronted battle-hardened Japanese troops under General Tomoyuki Yamashita in the mountains outside Manila.

On February 20, the 2nd’s 7th Cavalry Regiment marched over the concealing ridge on the west bank of the Marikina River, crossed it, and seized Taytay the following day, while the 8th Cavalry Regiment occupied Tagig. Two days later, on the left, the 6th Division had a similarly easy time taking Montalban and crossing the two-mile-wide valley unmolested by Japanese artillery.

As the line proceeded to advance in the days ahead, however, the free pass came to an end. The American troops quickly encountered the difficulties that would face them throughout the campaign against the southern Shimbu Line. The initial, lower hills tended to be open, grass-covered slopes that allowed little opportunity for concealment beyond the bamboo- and brush-covered draws, and the barren summits were open to Japanese artillery and mortar attacks. But the going got even rougher as the Americans advanced eastward into higher, more desicated terrain, with hills of 1,200–1,400 feet, and topping 2,000 feet farther east. They were characterized by heavy woods, numerous streams, deep gorges, and sheer cliffs.

It was in this first chain of hills—Mounts Oro, Pacawagan, Mataba, and Yabang—that the Japanese had placed their initial defenses. They had managed to stock these positions with a wide variety of weapons, from rifles, mortars, machine guns, and grenades to antiaircraft artillery, antitank guns, 105mm howitzers, and 155mm guns. Some of the high-velocity guns had been captured from the Americans in Manila or at Clark Field three years earlier.

The Japanese also made use of 200mm and 447mm rockets. The former was propelled using frames of six parallel members about five feet long with three rockets fired simultaneously between the members. The rocket had seven propellant charges, and the shells were loaded with picric acid. They had a range of four to five miles. Although the Americans considered these rockets inaccurate, the concussions were powerful enough to cause numerous casualties in the 6th Division’s 20th Infantry.

Weapons were generally deployed from a network of mutually supporting caves on both forward and reverse slopes. The sophistication of these defenses indicated that preparation had begun long before the invasion. Closely spaced to provide interlocking fire, such caves typically had a 10-foot shaft at the foot of which was a tunnel leading to a compartment. Four or five lateral tunnels led from the compartment, though one was discovered with 32 entrances. Each entrance was protected by sandbag or log bunkers, machine guns, and natural camouflage. Artillery would pop off a few rounds at the Americans and then withdraw into the caves for protection. A typical cave might hold 25 men.

The Americans had encountered such defenses since the New Guinea and Solomon Islands campaigns and were evolving their tactics to counter them. A distinguishing characteristic of the Shimbu campaign was the Americans’ heavy reliance on incendiary weapons. According to U.S. Army historians Brooks Kleber and Dale Birdsell in The Chemical Warfare Service: Chemicals in Combat, infantry commanders in previous campaigns had regarded the smokescreens provided by white phosphorous (WP) mortar shells as being superfluous in thick jungle cover. But the peaks of the Sierra Madre provided the Japanese with excellent observation points, so the ability of WP to conceal Allied activity became suddenly appreciated.

These shells also proved their effectiveness at inflicting casualties and burning away camouflage. This, combined with a shortage of high explosive (HE) shells, caused the ratio of WP to HE to rise from 20/80 to 40/60. As an example, some of the heaviest 4.2-inch mortar fire in the Pacific War would occur in the vicinity of Mount Mataba on April 6, when soldiers from the 82nd Chemical Mortar Battalion put up a 6,000-yard smokescreen. They maintained the screen for eight hours, at a rate of 16 rounds a minute for the first hour and 10 per minute thereafter, until they ran out of ammunition.

Major General Leonard F. Wing, commander of the U.S. 43rd Division, confers with General Walter C. Krueger, commander of the Sixth Army.
Major General Leonard F. Wing, commander of the U.S. 43rd Division, confers with General Walter C. Krueger, commander of the Sixth Army.

The other incendiary weapon characteristic of this campaign was a recent invention, the napalm bomb. This was an improvement over earlier gasoline bombs in that the soap-based napalm acted as a thickening agent that allowed the gasoline to burn long enough to transfer heat and fire to the target. A 165-pound bomb dropped from a plane would burn an oval of about 100 by 300 feet, denying camouflage to the enemy.

According to prisoners, the Japanese feared these “fire bomb” attacks more than anything else. They would sometimes leave even deep caves to emerge into the open, even though this left them vulnerable to the fragmentation bombing that followed. But soldiers had little chance whenever the technique of “skip-bombing” proved successful. If a plane got low enough, it could cause the bomb to skip along the ground like a stone tossed across water. This could be tremendously destructive if it bounced into a cave entrance; even if not killed directly by the bomb, many troops died due to the instant deoxygenation of the air.

The Japanese could intercept pilot messages sent in the clear, but they were unable to decipher any codes; nor were they able to jam radio frequencies. They were also unsuccessful in confusing attacking aircraft by firing smoke into American lines. However, the smoke from the napalm bombs would rise more than a half mile, so American pilots would have to make an upwind approach to maintain visibility.

Still, aircraft hits were not enough to do the job. Typically, the soldiers still had to go in themselves and seal the caves. Immediately after a bombing or shelling, they would toss in WP grenades or use flamethrowers or bazookas at the entrances, and then ignite several hundred pounds of TNT. When the last entrance was sealed, the Japanese would suffocate.

These flamethrower teams were supported by artillery and direct fire from tanks and tank destroyers. In a ground role, 40mm and 90mm antiaircraft guns and 105mm howitzers were heavily used, both for reducing caves and reinforcing the field artillery (which the Japanese later claimed was employed too predictably to be fully effective). In this mountainous terrain, the American antiaircraft gunners learned to fire their shells in a straight line rather than allow the usual loft.

In one 48-hour period, the 2nd Cavalry Brigade took 137 caves and blew up 446 outlets. However, by March 4, they were still miles short of Antipolo, while the 6th Division was having a tough slog in its campaign against Mounts Pacawagan and Mataba. Both units had suffered heavy losses and received no replacements. Griswold felt that he had no choice but to shorten his lines, concentrating on the Noguchi Force and the southern part of the Kobayashi Force, hoping to eventually outflank both by taking the Bosoboso Valley and thus severing the Shimbu supply lines. He still did not know about Yokoyama’s reserve troops in that valley or about the new road that would facilitate their movement.

Griswold did know that he was about to lose the 2nd Brigade and its parent division, the 1st Cavalry, to reassignment in southern Luzon. To replace it, Krueger could have chosen the 38th Division, which had seen little combat since finishing a tough campaign at Bataan’s ZigZag Pass on February 15, but, on March 7, he decided to go with the 43rd, a more experienced division, even though it had spent the last 10 days helping the 40th fight the Kembu Group and would get little rest. Its 169th RCT would remain on the Kembu front, while its 103rd Infantry would move to the Shimbu Line immediately, ahead of the rest of the division.

Major General Edwin Patrick commanded the U.S. 6th Infantry Division.
Major General Edwin Patrick commanded the U.S. 6th Infantry Division.

With the arrival of the 103rd, Griswold decided not to wait for the rest of the 43rd. For two days, he launched a series of bombing attacks, with particular attention given to an area near Antipolo. On March 8, with little in the way of reserves, he sent the 6th Division and the 1st Cavalry (now reinforced by its 1st Cavalry Brigade, brought in from Manila) in an attack against Antipolo. The latter division encountered heavy resistance that included mortar, artillery, and rocket fire, and suffered heavy losses but pressed ahead and secured the high ground north and south of the town. The 103rd replaced the 2nd Brigade on March 11 and entered Antipolo unopposed the following day. Attached mechanized forces then made a 25-mile dash to the rear of strong Japanese positions near Teresa, thereby preventing the Japanese from fighting a delaying action back to prepared positions east of the Morong River Valley.

Meanwhile, the 6th Division, pressing against the hills overlooking the Marikina River Valley east of Montalban, also faced heavy opposition. Well supplied with artillery, Japanese defenders repeatedly made intense nighttime attacks that would reverse American advances made during the day.

The Americans Had Lost 295 Killed Against More Than 3,300 for the Japanese.

This resistance managed to hold the 6th Division’s left wing to only minor gains, but its 1st Infantry, on the right and facing less opposition, did break through to seize a strategic ridge rising to Mount Baytangan. Then, against more stubborn resistance, it penetrated deeply between the Kobayashi and Noguchi Forces to cut supply trails and seize an observation post.

This was too much for General Yokoyama. He ordered the Noguchi Force back to second-line defenses and drew up complicated plans for a counterattack on March 12, primarily against the 6th Division’s salient. However, his three-pronged, seven-battalion assault plan was far too ambitious given the quality and deployment of his men and materiél, the rugged terrain, and the poor communications.

Unknown to Yokoyama, the 6th was planning its own offensive that day. Air and artillery bombardment disrupted the already poor Japanese transportation and communications so effectively that, when the Japanese attacked, the 6th was not even aware of it. It merely took note of persistent night infiltration by small groups of Japanese from March 11-15.

Meanwhile, the 6th’s attack was proceeding well, although they did lose their commander, Maj. Gen. Edwin Patrick, to a hidden machine-gunner. The 43rd Division had taken over for the 1st Cavalry just in time to exploit the withdrawal of the Noguchi Force, a process that left the latter’s southern flank largely exposed. So, in spite of its difficulties, XIV Corps had made substantial progress, having driven a wedge between the Noguchi and Kobayashi Forces and having gone far toward turning the Shimbu Group left. The Americans had lost 295 killed against more than 3,300 for the Japanese.

A Japanese fuel dump, hit by U.S. naval gunfire prior to the landings on Leyte by the U.S. 1st Cavalry Division, goes up in flames.
A Japanese fuel dump, hit by U.S. naval gunfire prior to the landings on Leyte by the U.S. 1st Cavalry Division, goes up in flames.

The XIV Corps now had new assignments to the south. On March 15, responsibility for the Shimbu operation passed to XI Corps, under Lt. Gen. Charles Hall. He sent the 43rd Division forward in a two-pronged attack. Its right column found little resistance, and by March 22 reached Pililla, about 12 miles southeast of Antipolo. But, at this point, Yokoyama was more concerned about the left flank of the Kobayashi Force, which he ordered held at all costs. So, the bulk of the 43rd, pressing up the Morong River Valley toward Mounts Quitago, Tanauan, and Yabang, and the right wing of the 6th, advancing toward the Mt. Baytangan/ Purro/Lamita line southeast of Wawa Dam, found the going a lot rougher. A network of well-camouflaged caves had to be disposed of one by one. When a strongpoint could not be reduced, troops had to be detached, which reduced the strength of the main attacking force and considerably slowed the advance.

On March 17, when the 6th’s 1st Infantry was driven back by heavy Japanese 150mm mortar fire and sweeping automatic weapons fire, they adjusted their tactics and proceeded by a series of patrol actions, followed by consolidation and mop-up. Although safer, this further slowed the advance. By March 22, the 43rd had only gotten as far as Mounts Quitago and Tanauan, while the 1st Infantry was still trying to take Mount Baytangan. The 6th’s 20th Infantry, on the left, had similarly bogged down before less well organized but diffuse resistance in its drive toward Mount Mataba, and a diversionary attack by the 63rd resulted in heavy U.S. casualties.

This slow progress was costing the Americans 55–60 casualties in each regiment daily— an attrition rate that was about to bring the advance to a halt. “For days the only real gain was time,“ says an XI Corps history. “Time to push roads up through the hills, to resupply and evacuate the wounded, roads to allow tanks and M-7s to be brought up over the hills for direct support of the Infantry.”

At this critical point, Yokoyama decided that the situation on his left was hopeless, and he began withdrawing his troops in that area further into the mountains. Over the next few days, surprised American forces advanced quickly. On March 24, the 43rd seized Mount Yabang and, on the 27th, the 6th took Mount Baytangan. In the days ahead, the Americans would continue to press forward in the general direction of Wawa Dam from the south and east while, farther south, cutting off Japanese supply routes from the Bicol Peninsula. While fierce fighting lay ahead in isolated strongpoints, the southern flank of the Shimbu Line had finally been turned and most of the Noguchi Force destroyed.

The gains had not come easily. As Army historian Robert Ross Smith states in Triumph in the Philippines, the campaign by XIV and XI Corps could have achieved the results more quickly had they been at full strength, instead of “holding out scant reserves and expecting normal results from generally understrength units.” Furthermore, he credits Yokoyama for holding out so long, given “the heterogeneous nature of [his] forces, the preponderance of second-class, ill-trained troops, the inadequate strength of the Noguchi Force for the mission assigned it, poor communications, and the gradual deterioration of control all across the group’s southern front.” He cites Yokoyama’s well-conceived defenses, advantages of terrain, and, not least of all, “the willingness of the Japanese soldier to fight and die in place no matter how hopeless his situation.”

Changes were in order. Since striking north from Mount Baytangan on March 28, the exhausted, understrength 6th Division had made only negligible progress. On April 3, General Hall shortened its front, which released the bulk of its relatively fresh 63rd Infantry for use in a new attack against Mount Mataba. It also allowed him to focus on his northern flank, which heretofore had only been lightly screened by patrols of the 112th Cavalry RCT. The 112th had been charged with probing enemy defenses in the Ipo Dam area; now, with intelligence reports indicating increased enemy activity, Hall wanted to conduct a reconnaissance in force toward the dam. He paired the 112th with the 43rd’s 169th RCT (newly retrieved from combat against the Kembu Group) to form a task force for this purpose and dubbed it “Baldy Force” in honor of its follicle-challenged commander, Brig. Gen. Julian Cunningham.

The most direct approach to Ipo Dam was along Metropolitan Road, a two-lane road that led through steep palisades at Bigti and then four and a half miles east to the dam. The limestone palisades posed a particular problem, since they were honeycombed with Japanese-occupied caves. But an attack on either flank would have to advance over terrain characterized by jumbles of rock and brush outcroppings that provided ideal sites for enemy caves and camouflage. A reconnaissance was necessary, but on the ground, since Japanese antiaircraft defenses limited use of liaison planes.

On the heels of an air strike, Sherman tanks of the 754th Battalion prepare to attack Japanese positions in the area of the Ipo Dam on Luzon.
On the heels of an air strike, Sherman tanks of the 754th Battalion prepare to attack Japanese positions in the area of the Ipo Dam on Luzon.

On April 7, the reconnaissance advanced, with the 169th coming from the southwest and the 112th from the west. The 112th, testing the defenses astride Metropolitan Road, encountered much stiffer resistance and was stopped by intense mortar and artillery fire on the 10th some 7,000 yards west of the dam. The Japanese counterattacked continuously for 24 hours. The 43rd Division history relates, “The aggressiveness and accuracy of enemy artillery in this area was extraordinary. Any unusual activity by our infantry, or other elements, brought immediate shelling.” An intelligence report surmised the presence of “at least 2 Bns of artillery,” including 120mm antiaircraft guns and even a 170mm naval gun. The reconnaissance was called off on April 11, having established that, while the road to the dam presented a stiff challenge, the southwest approaches were but lightly defended.

This knowledge would be useful when the time came, but, as far as Krueger was concerned, that time was not quite at hand. He recognized that XI Corps would require more than its present strength for further attacks against the dams and so began planning to shorten its lines by transferring its southernmost assignments to XIV Corps. In the meantime, the hill-by-hill advance toward Wawa Dam continued. The 43rd drove north from Bosoboso to attack forces on Mount Mapatad, and the 6th secured Mount Mataba on April 17, putting it in a position to attack Mount Pacawagan, just two miles from the dam, from the south as well as the west.

On April 18, Krueger reassigned the southern Infanta/Santa Maria/Famy/Siniloan zone to XIV Corps. There had been indications that enemy remnants had been escaping from those areas to Infanta and thence to the Shimbu Line; XIV Corps would need to seize Infanta to cut them off.

This must have been welcome news to the hard-pressed General Hall. But then, the following day, Krueger received a radio message from MacArthur that revealed that the Japanese were not the only ones with communication problems.

It is Not Clear How Krueger Learned of Ipo’s Primacy nor What Steps He May Have Taken to Inform MacArthur

MacArthur indicated that the water shortage was now becoming acute, “cutting daily consumption in Manila to one half and depriving south side of river of any city water except what is carried in tanks. In summary CMA water shortage is bringing back danger of epidemic of enteric disease from which city was apparently escaping. Outbreak of real magnitude might well prove great military disaster. This situation will be remedied as soon as the reservoir in the Montalban area is secured. What is your estimate as the time when this will be accomplished?”

The phrase “reservoir in the Montalban area” stumped Krueger. The Novaliches and San Juan reservoirs had been in American hands for over two months; the water installation that was closest to Montalban was Wawa Dam. But, at some point in the campaign, Krueger had learned something that MacArthur apparently still did not know: Wawa Dam was no longer a part of the Manila water system.

Since the completion of Ipo Dam in 1938, Wawa Dam had been disconnected in order to serve local irrigation projects. Ipo Dam constituted a third of Manila’s water supply. Even if Wawa Dam were reconnected, it could only supply 15 percent. Two days after receiving MacArthur‘s plea, Krueger radioed back, “Do you mean Ipo Dam?”

Smoke and flames engulf Japanese defenses in the rugged terrain near Ipo Dam following an attack by fighter bombers of the U.S. Fifth Air Force. The effectiveness of the attack allowed ground troops to advance two miles virtually without resistance.
Smoke and flames engulf Japanese defenses in the rugged terrain near Ipo Dam following an attack by fighter bombers of the U.S. Fifth Air Force. The effectiveness of the attack allowed ground troops to advance two miles virtually without resistance.

Krueger’s puzzled response seems to indicate that he thought that MacArthur was aware of the situation. It is not clear how Krueger learned of Ipo’s primacy, what steps he may have taken to inform MacArthur, or why he did not go out of his way to discuss with him whether a change in tactics was called for. Nor is it clear why MacArthur’s staff was not aware of the situation from the beginning, considering that the Americans had been governing the Philippines in 1938.

Krueger may not have seen any percentage in pressing the issue. In January, as his men battled stiff challenges from the Shobu Group en route to Manila, MacArthur had taken him to task for an advance that he considered plodding and that Krueger thought sensible, given the manpower shortage. Now, once again, Krueger had no reserves to throw at a new priority. His men were thoroughly engaged in an effort to roll up the Shimbu Line from the south, which made good strategic sense in that it cut off reinforcements. Further, the fact that MacArthur had raided the Sixth Army after the decision to seize the dams was hardly an advertisement for urgency.

In his 1953 account, From Down Under to Nippon, Krueger suggests that he was on it. He states that Hall proposed creating Baldy Force “when I discussed … the great importance of the early capture of Ipo Dam” and that “instructions to that effect” had already been given prior to MacArthur’s plea. The nature of those instructions is not mentioned. While Ipo Dam may have been looming larger in his thinking, this was, once again, insufficient for MacArthur, who returned a terse reply on April 22: “Capture of Ipo Dam would provide definitive solution for Manila water supply problem and is highly preferable as objective.”

There was no practical way to achieve this except by redeploying an already active division; the reassignment of some XI Corps responsibilities to XIV Corps made this possible, but still not without a lot of musical chairs. Hall ordered the 43rd Division to move north to Ipo Dam. Baldy Force would be dissolved, with the 169th RCT rejoining the 43rd and the 112th RCT assigned to the 38th Division along the extreme south of the Corps zone, on the north shore of Laguna de Bay. As of April 30, the 38th, which had been continuing to grind down the Kembu Group, would be the new player in the area. It would replace the 43rd, along with the 6th.

The 6th had been making significant gains. After the exhausted 20th Infantry had been replaced by the 37th Division’s 145th Infantry, it had eliminated most of the opposition on Mount Pacawagan by the end of the month— and, as a whole, had eliminated 3,000 Kobayashi Force soldiers in April. However, the cost had been high.

Historian Smith states, “Morale was down, men and officers alike were tired and worn, and all units were sadly understrength, especially in combat effectives. Since 22 February the 6th Division had suffered approximately 1,335 combat casualties—335 killed and 1,000 wounded—and over three times that number of men had been evacuated from the front lines either permanently or temporarily for non-combat injuries, sickness, and psychoneurotic causes.”

Malaria had increased for those fighting in the mountains, and an outbreak of flies that fed on rotting bodies led to a sharp increase in bacillary dysentery, which peaked by the end of April. In Crisis in the Pacific, historian Gerald Astor quotes infantryman Carlie Berryhill: “My regiment, the 63rd Infantry, had 112 days of continuous combat without a break. We wore our clothes sometimes for a month or longer without a change. It rained so much they never had much time to dry on your body. I remember a couple of times when I removed my socks they would just tear off in pieces.”

The 6th’s 20th Infantry would help garrison Manila, while the remainder would replace the 38th Division in the Zambales Mountains. Given the troop shortage, patrolling the rugged terrain for stray Japanese would have to suffice as a “rest period” for the 6th Division.

The crew of an 8-inch howitzer nicknamed “Comanche” fires at pockets of Japanese resistance near Ipo Dam.
The crew of an 8-inch howitzer nicknamed “Comanche” fires at pockets of Japanese resistance near Ipo Dam.

Now, Maj. Gen. Leonard Wing, the 43rd’s commander, turned his attention to the attack on Ipo Dam. The Baldy Force reconnaissance had revealed the difficulty of advancing directly up the well-fortified Metropolitan Road from Bigti toward the dam. At the same time, the light resistance south of the road indicated that perhaps Yokoyama did not expect a large attack to proceed over such forbidding ground. If so, Wing decided to show him otherwise.

The main thrust of the attack would be led by the 103rd Infantry, on the division’s right. It would use a ridgeline from Mount Katitinga, four miles south of the dam, as its main route of attack. To its left, the 172nd Infantry would advance east-northeast along a two-mile front before turning north to attack Osboy Ridge, which runs parallel to the road. From there, they would advance north about to cut the road and isolate enemy forces at Bigti, which would be pressed from the west by the 169th.

The Americans were greatly helped by Filipino guerrillas. From the very beginning of the Japanese occupation, numerous bands had been active throughout the Philippines. They ran the gamut from highly effective, disciplined groups to common criminals. But one of the outfits most useful to the Americans was Marking’s Fil-American Yay Regiment, better known as Marking’s Regiment, a group of Filipino guerrillas about 3,000 strong. This group was headed by Colonel Marcus V. Augustin, a former Manila-Antipolo bus driver who had escaped Bataan and chosen “Marking” as his guerrilla name.

Augustin ran the organization with his common-law wife, Yay (rhymes with “high”) Panlilio, a Denver-born Irish-Filipina who, as a 20-year-old, had come to the Philippines and started a family and a successful career as a journalist. She was working as a U.S. Army intelligence agent when the war broke out. Together, they led a group of followers that bedeviled the Japanese for three years, harassing small groups and transmitting information to MacArthur’s headquarters.

Since the summer of 1944, when American submarines began smuggling in supplies and liaison officers, Marking’s Regiment had been working directly under the U.S. Army and had been active with the 43rd Division on XI Corps’s southern flank.

A Total of 250,000 Gallons of Napalm was Dropped on Enemy Positions Defending Ipo.

Unlike guerrilla bands in the Zambales Mountains, which one intelligence memo described as “not stable,” Marking’s Regiment had been described in another memo as a “pro-American” group. It stated that it was “comparatively well armed but supplies of ammunition, food, and equipment are extremely limited. They are familiar with the terrain where they operate and are valuable as guides and on some scouting missions. Their combat efficiency is probably low and will be best used in conjunction with U.S. troops rather than independently.”

In the Ipo Dam campaign, Marking’s Regiment would be under the direction of Brig. Gen. Alexander Stark, the assistant commander of the 43rd. Its role was to attack the northern flank, largely as a feint to confuse the Japanese. Because of this secondary status, there were no plans to give it significant artillery or air support.

The Japanese defenders grudgingly gave ground before American thrusts through rugged terrain toward the dams that held water vital to the city of Manila.
The Japanese defenders grudgingly gave ground before American thrusts through rugged terrain toward the dams that held water vital to the city of Manila.

The regiment would split into a North Force and a South Force of about 1,500 men each. Starting near Norzagaray, northwest of Ipo, the South Force would proceed up the Angat River Valley toward the dam. The North Force would make a wide envelopment toward Mount Kabuyao, north of the dam, and then attack due south.

For the month of May, the Fifth Air Force’s 309th Bomb Wing, which was assigned to XI Corps, would be primarily engaged in providing close support of ground troops, and preparing for the Ipo campaign would be their first major assignment. For three days before the attack, 238 heavy and fighter bombers carried out pattern-bombing against five main areas. A total of 250,000 gallons of napalm—the largest amount used anywhere in the Southwest Pacific area up to that time—was dropped on enemy positions defending Ipo.

There was, however, one unintended effect of these attacks. Yokoyama had ordered a battalion to move south to the Wawa area to participate in counterattacks—and Maj. Gen. Osamu Kawashima, thwarted by the bombings from quickly assembling his troops and sensing that something was brewing, took it upon himself to halt such movements. This would not be good for the 43rd Division, but at least it helped the 38th, which had begun its own offensive toward Wawa Dam.

Meanwhile, Wing moved his men forward. Among all units, surprise was vital. Smith writes that the division “moved northward in small increments between 2 and 5 May, assembling behind a line of outposts the 169th Infantry maintained. The division kept reconnaissance to a bare minimum, and units deployed along their lines of departure under cover of darkness in preparation for jumping off during the night of 6-7 May.” Radio silence was maintained, except for the 169th, whose presence, of course, was already known to the Japanese.

The attack would begin at night. This was risky, especially over ground that had not been thoroughly reconnoitered. But the earlier Baldy Force probe, along with successful night attacks in the Antipolo-Montalban area, convinced the Americans that the risk was worth it to achieve surprise.

On the evening of May 6, the Americans launched their regularly scheduled night harassing artillery. Then, at 10 pm, with a sky harboring occasional showers but otherwise offering fair to good visibility, they attacked. As the division artillery supplemented the light moon with WP shells, the 103rd Infantry moved forward, ultimately advancing to a point less than three miles from the dam. The 172nd also attacked northeast but progressed more slowly, having to endure the roughest terrain of all due to the guides losing their way.

Still, by day’s end they had come to a point near the foot of a rocky ridge two miles southeast of Bigti. North of the Angat, Marking’s North Force met no organized resistance as it marched over seven miles east to Bayabas, only one and a half miles northwest of its initial objective of Mount Kabuyao. Apparently, not even Kawashima had been expecting a night attack; the only significant resistance was encountered by a company of Marking’s South Force, which was repulsed by part of the Kasama Battalion at Hill 535, on the south bank of the Angat three miles north of Bigti.

At daybreak, the 169th began an eastward movement against the Japanese fortifications north and south of Bigti, while the other units continued their gains. Company-strength patrols would continually probe and withdraw, in different locations, in a successful effort to draw the enemy away from the other regiments. Dive-bombers on air alert targeted antiaircraft guns, thereby allowing the Americans to use artillery liaison planes.

By the spring of 1945, the situation on Luzon was hopeless for the Japanese. Subjected to relentless pounding by American air and ground forces, they were compelled to withdraw into an ever tightening perimeter.
By the spring of 1945, the situation on Luzon was hopeless for the Japanese. Subjected to relentless pounding by American air and ground forces, they were compelled to withdraw into an ever tightening perimeter.

Now, to the southeast, opposition weakened, and the attack continued through the night and the following days until, by late on the 11th, the 103rd was deployed in a south-southeast arc two miles from the dam. Its leftmost position was overlapped a half-mile north by the 172nd, which extended to Fork Ridge two miles east of Bigti and directly south of Osboy Ridge, which overlooked Metropolitan Road where the Kawashima Force had been putting its main defenses.

Wing eyed Osboy Ridge with interest. By maintaining their principal defenses along the approaches to Metropolitan Road, the Japanese had allowed the other American/Filipino units to make solid advances. In particular, Marking’s Regiment, which was to be used as a feint, had made startling progress, advancing to Four-Corner Hill, less than two miles north of the dam. Indeed, the entire operation was turning into a double envelopment.

With the Japanese beginning to withdraw troops from the Bigti/Osboy area to meet the threat from the 103rd, Wing directed the 169th to increase the strength of its demonstrations and launch a limited attack against Osboy Ridge. At the same time, he gave artillery support to Marking’s Regiment, which broke through at Four-Corner the following day.

Progress then began to slow. As they advanced closer to the dam, the Allies encountered rougher terrain, automatic weapons fire, heavy mortars, and extremely accurate artillery fire. They also encountered unseasonably early rains, which especially bogged down the heavily outfitted and mechanized Americans. Daily advances were less than a thousand yards; and the 169th made only slight progress against the well-fortified Osboy Ridge.

Even Hill 535, at the extreme northwest of Japanese positions, was still out of reach. Lieutenant Henry Lashway of the 169th’s A Company described the reception his company got from its opponents when while relieving another company on Hill 525, one kilometer away: “They knew exactly when we took over the position and we didn’t get settled before we were hit by considerable rifle fire. When I first got there, I started to clean my carbine and set my canteen cup and cartridge belt on the top of a rock ledge. They shot it off. One of the sergeants got a bullet hole in his cap and another a hole through the wrinkle of his shirt. At night there was lots of hand grenade throwing on both sides, but the jungle was too thick for many grenades to get through. We could tell when they were coming because they activated their grenades by tapping them on their helmets. Our grenades were activated when we pulled the pin and released the lever. After we let them go they exploded in five seconds. There was always a “snap” five seconds before the explosion and they knew when ours were coming. It was while we were on this hill that we received a new grenade which had no “snap” and exploded three seconds after throwing. I don’t know whether they received any casualties from this or not—but they must have been surprised.”

Surprise was also the norm at the Japanese command level, for its ability to assess and communicate situations was growing weaker. Yokoyama still did not understand that Kawashima Force was under attack by a reinforced division. Having failed in his earlier counterattack against the 38th Division, he ordered Kawashima to send more troops to assist the Kobayashi Force in a new counterattack for May 14. Kawashima tried to persuade him otherwise, but to no avail. On the night of May 12, under the cover of attacks against the 103rd and 172nd Regiments, he moved the bulk of his Kasama Battalion south.

“It Took Twenty Hours to Carry Wounded From Battalion Positions to the Nearest Surgical Echelons.”

The results were predictable, as the Allies swept forward on the 13th. By the end of the day, the 103rd was only about three-quarters of a mile from the dam, and Marking’s men were slightly closer on their side. Now Kawashima, without checking with his superior, ordered the Kasama Battalion back. He needn’t have bothered; its namesake, Major Tetsuyuki Kasama, had learned that his southern route had been cut off and had already started back. Kasama tried and failed to regain lost positions, but did slow the American advance on May 14.

A rare sight, three Japanese prisoners captured during the fighting around the Ipo Dam sit on the ground surrounded by their American captors.
A rare sight, three Japanese prisoners captured during the fighting around the Ipo Dam sit on the ground surrounded by their American captors.

Yet, only so many holes could be plugged. While the Japanese were preoccupied south of the dam, a guerrilla patrol reached the dam on the night of May 13. Although it was too small a force to take the dam, the patrol returned with the information that it was still intact.

There was little the Americans could do at the moment. As Krueger would later write, “On 13 and 14 May it rained in torrents. The roads the engineers had built to follow up the advance of the 103d and 172d Infantry Regiments became completely impassable. Trucks carrying ammunition, rations and medical supplies were mired hub-deep. The lightly wounded dragged themselves to the rear as best they could, while the seriously wounded waited patiently in the hope that they would eventually be cared for. Artillery, tanks and mortars, which had been pushed forward close behind the advancing infantry, were immobilized. Ammunition expenditure had to be curtailed until the road could be made passable again.

“About 1,000 Filipino cargadores were employed to fill the gap, but while they did their best their efforts were but a drop in the bucket. It was a three-day march for them to reach the front lines.

“Air drops helped the supply situation somewhat, but nothing much could be done to meet the most critical need, the evacuation of the wounded. It took twenty hours to carry wounded from battalion positions to the nearest surgical echelons. On 14 May a portable surgical hospital was dragged forward by tractors and manpower until it became hopelessly mired, but it still took ten hours to transport a wounded man from the front back to this establishment.”

Clearly, Metropolitan Road had to be opened. And, with the reduction of Japanese forces from the Bigti area, now was the time for the 169th to attack along the road in full force and take the pressure off the other regiments—particularly the 172nd, which was bogged down on Fork Ridge but in position to take several hills farther up the road.

Rain delayed all operations on the 15th. The following day, the five-square-mile Japanese territory was attacked by the Fifth Air Force. The P-47 Thunderbolts and P-38 Lightnings went in first, at 50 to 100 feet, dropping 50,000 gallons of napalm in the Bigti–Osboy Ridge area. These were followed by P-51 Mustangs, which strafed and bombed any Japanese trying to escape.

The following day the action was repeated with another 62,500 gallons. Positions near Hill 804, midway up the road, and northwest of that point took the brunt of the attack, which was joined by A-20 Havoc bombers. A Fifth Air Force report describes the attack: “… 200 to 250 5th AF fighters came in low, wave after wave, four to eight abreast, with air and ground controllers giving target information and regulating traffic. At first, the closely spaced fighters found that smoke from preceding waves obscured the target. The problem was overcome by directing the bombing runs downwind, with each successive wave dropping its bombs on the near side of the bursts from the wave which preceded it. The fighter bombers followed each other at 10- to 15-second intervals. A-20’s then came in, showering the area with parafrags and winding up with a thorough strafing.”

A Japanese tank, knocked out by infantrymen of the 43rd Division, smolders on a dirt road on January 17, 1945.
A Japanese tank, knocked out by infantrymen of the 43rd Division, smolders on a dirt road on January 17, 1945.

With this protection and that of 40- and 90mm antiaircraft guns and 4.2-inch mortars, the 169th took Bigti and used bamboo scaling ladders to seize the palisades overlooking the north side of Metropolitan Road. Opposition was light, since their foes had been withdrawn earlier to replace the Kasama Battalion during its ill-fated mission to the south. The 169th’s primary obstacles were the boulders that the air strikes had blasted from the cliffs. Meanwhile, the 172nd drove the enemy off Fork Ridge while enveloping the Japanese from the east.

Now, the 103rd seized Hill 860 overlooking the dam and sent a small patrol down to its southern end to investigate. Finding little activity, it returned quickly. Shortly thereafter, Marking’s Regiment, having dispatched its remaining opposition in hand-to-hand combat, sent its own patrol down on the opposite side of the Angat. It waded across the river and, at 1:30 pm, raised the American flag over the powerhouse on the south bank. Ipo Dam was taken.

“I Never Did Dare to Tell Krueger What Impelled Me to Hurry up His Attack on the Ipo Dam.”

The air-ground coordination had played a crucial role in this campaign, and Krueger gave due credit to the Fifth Air Force, saying that its attacks had “made possible the early capture” of the dam. What he did not know was that its commander, Lt. Gen. George Kenney, had his own strategic reasons for the final attacks, according to Kenney himself. In his 1949 memoirs, General Kenney Reports, he writes: “I told [Gen. Ennis] Whitehead that I wanted water in [Kenney’s Manila] pool so that I could invite him down for a swim before dinner sometime and suggested that he get in touch with Krueger and offer to put a couple of hundred planeloads of Napalm on the Jap positions and burn them out. I thought if the job was done on a big scale the Nips would not have time to blow up the dam and Krueger’s troops could then turn the water on, Manila’s water problem would be solved, and we could go swimming…. I never did dare to tell Krueger what impelled me to hurry up his attack on the Ipo Dam.”

Notwithstanding Kenney’s claims, it remains a mystery why Kawashima allowed the dam to be taken intact. Certainly, it was no gift. The gate was wired with hundreds of pounds of TNT, and, on the day of its capture, four Japanese were killed at the site of the detonating device. Furthermore, two small banzai attacks were repulsed that night.

Again, a communications problem would seem to be the most likely explanation. Either late on the 16th or early on the 17th, Kawashima had given up on the dam and ordered the withdrawal of his forces to a point three miles farther east. But the dam was not blown—and it was not the first to be left intact. In February, the Japanese had failed to destroy the Novaliches Reservoir, Balera Filters, and San Juan Reservoir, in spite of indications that they had planned to do so. Perhaps, at that time, they could have been excused for underestimating the rapidity of the U.S. advance. But there was no such excuse now. Considering that the final attack had taken place over 11 days, and that the Japanese had no hope of reinforcements, the failure to destroy Ipo Dam was a major blunder.

Now, there was just the mopping up. On May 19, the 169th and 172nd captured Osboy Ridge and opened up Metropolitan Road all the way from the dam to Novaliches Reservoir. In the days ahead, the 225th AAA Searchlight Battalion looked for stragglers by lighting up the ravines and valleys. By May 21, all organized resistance was over.

That point was fast approaching for the Japanese at Wawa Dam, as well, for they had not only been suffering directly from the attacks of the Americans but from their own tactical errors, engendered by an inability to gather intelligence and understand what the Americans were up to.

Some fanatical defenders decided to fight to the death in Manila. American soldiers of the 1st Cavalry Division trudge past the bodies of several of the Japanese dead.
Some fanatical defenders decided to fight to the death in Manila. American soldiers of the 1st Cavalry Division trudge past the bodies of several of the Japanese dead.

The Americans’ April advances notwithstanding, Yokoyama had been so unimpressed by their effort that he thought that XI Corps had decided to move most of its troops to northern Luzon. If so, this would have meant that Yokoyama had failed in his mission to keep them pinned down in his sector. Determined to avoid this, but knowing he was too weak to retake ground, he planned for limited counteroffensives beginning May 10 that would at least sow confusion in the American lines.

Instead, the confusion was his own. He had not only failed to realize that the Americans were preparing to attack Ipo Dam, but he also had not anticipated the 38th’s May 4 offensive. After the 145th Infantry (now attached to the 38th Division) finished securing the most vital parts of Mount Pacawagan, it was poised to attack east toward Wawa Dam. The 38th’s 152nd Infantry was to support them by moving north along Woodpecker Ridge (so named after the sound of the Japanese 7.7mm heavy machine guns, which were present in abundance). The May 4 attack produced only mediocre results but caused the Japanese to weaken their defenses at the nearly impregnable Mount Binicayan, overlooking Wawa Dam, thereby allowing it to be seized by the 145th on May 9.

The Japanese counteroffensives themselves, according to a 38th Division history, “consisted mainly of night infiltration attacks using automatic weapons and knee mortars, and several daylight counterattacks against our units. In some instances, these attacks were supported by artillery and heavy mortars, but these weapons were soon spotted and silenced by our own artillery.”

However, troops were kept on edge by the nighttime infiltrations through the permeable front line; attacks could come from areas that had been previously cleared. They were always repulsed, so Yokoyama called them off on May 15. His forces at Woodpecker Ridge, however, did not get the message for nearly a week; the 152nd had to make seven attempts to take the crest before succeeding.

Improvisation and innovation were the norm as the 38th became the laboratory for a variety of new weapons. These included the 57mm and 75mm recoilless rifles (also used by the 43rd), which were highly valued for targets within 2,500 yards, because of their low silhouette, accuracy of fire, and power of impact. However, supplies were not sufficient to allow widespread distribution. Less satisfactory were the 4.2-inch recoilless mortars; they were inaccurate, had little mobility, and required a large clearance zone in the rear.

Also making their debut were tanks equipped with the Chemical Warfare Service’s new M5-4 flamethrower, which could discharge napalm-thickened fuel at a range of 105 to 130 yards, or about three and a half times the distance of ordinary fuel. They proved to be instrumental in clearing out wooded draws where machine gunners hid.

Ironically, the M5A1 light tanks themselves were obsolete. When the tank shortage in the U.S. portended delays in flamethrower installation, the CWS shipped its four prototype models to Luzon, where they were given to the 27th and 38th Divisions. An even greater mix of old and new were the 38th’s homemade catapults that fired jellied gasoline.

Finally, with Woodpecker Ridge and the Marikina-Bosoboso River confluence under American control, and the 151st Infantry having secured the northern approaches, the attack toward Wawa Dam began on May 27. Elements of the 149th Infantry, which had replaced the 145th, advanced up the narrow gorge. Supported by medium tanks and two flamethrower tanks, it eliminated enemy gun positions as it proceeded. The tanks, however, had limited maneuverability and withdrew after night fell.

Water rushes through a spillway at Ipo Dam. Capturing the reservoir intact meant that enough water would be available to supply American troops and Filipino civilians in Manila.
Water rushes through a spillway at Ipo Dam. Capturing the reservoir intact meant that enough water would be available to supply American troops and Filipino civilians in Manila.

The following day, the assault was led by Charles Oliver, a Texas native one year out of high school, who was handed a bazooka with a broken sight. Protected by two scouts and the rest of his company behind him, he moved forward, fired 28 shots at enemy installations, and made 28 hits. Spying a small cave farther up, he shot and missed twice. When he reached the dam, he said that the next time he wanted a bazooka with a sight on it.

Again, a dam had been captured intact. That evening, the troops defending Wawa Dam acted on orders issued by Yokoyama the day before to all Shimbu troops. It was time to withdraw. Yokoyama had lost nearly half his force—his best-trained and best-equipped soldiers. Of the remaining 26,000 men, Smith estimates, only 13,000 were in organized units. Another 5,000 were too sick or wounded to fight, and about 8,000 had disbanded into independent groups that were trying to make their way to northern Luzon or just roaming the area, scavenging for food. Perhaps Yokoyama thought his men would find food in scattered locations throughout the Sierra Madre.

“Anything Moving in the Pitch Black Night Would be Shot or Get a Grenade Thrown at Him.”

There was little chance of that. Japanese soldiers had found that, far from being a lush, fruit-covered paradise, the jungles of Luzon offered little in the way of sustenance. And, while Yokoyama had managed to evacuate plenty of weapons and medical supplies from Manila, the pre-harvest American conquest of the food-growing valleys in his region had severely diminished his supplies. The original ration of three pounds of rice a day was down to about six to eight ounces in the Kawashima Force and two ounces in the Noguchi Force. Soldiers were eating camote (sweet potato) leaves, roots, bark, and grass. The area’s fauna soon disappeared. One soldier was captured after successfully infiltrating a Filipino chow line.

Soon, some were going to even further extremes. When a Filipino official reported that 500 people had evacuated the barrio of Hacienda Patalao “for fear of being killed or eaten up by the Japs,” he was not indulging in hyperbole. POWs were speaking of acts of cannibalism, at least among their own.

This was confirmed by Shimbu Group surgeon Tadashi Moriya in his 1968 book, No Requiem. He spoke of “Japan guerri” who, in groups of two or three, would set upon a solitary soldier to kill and eat him. He attributed this to the fact that “the Japanese army drafted indiscriminately anybody who was physically fit for service, without investigating his character or past history. Among them were no small number of prison birds and ruffians.” For most Japanese, surrender was still not an option. As Tetsuru Ogawa, a veteran of the northern Luzon campaign, wrote in his 1972 Terraced Hell, the soldiers on the island “believed that the longer they held out, the more time Japan would have to prepare against enemy invasion, and hence the greater guarantee of the safety of their families. In this firm belief they fought and died.”

In June, the 38th Division, joined by the 169th RCT, continued to encounter resistance as it drove farther east from Wawa Dam. The attacks were now smaller banzai attacks, typically carried out at night by groups with small arms, grenades, and knee mortars.

This was enough to keep the soldiers jittery; they learned to never leave their foxholes, for the slightest noise could, and did, invite volleys of grenades from their comrades. One night, as the 169th’s Lieutenant Justin Raphael and his men hunkered down on Mount Ayaas, they spent the hours listening to the groans of a wounded Japanese soldier.

Along Luzon’s Villa Verde Trail, soldiers of the 38th Infantry Division seal the entrance to a Japanese-held cave with high explosives. The inhabitants were trapped inside and suffocated.
Along Luzon’s Villa Verde Trail, soldiers of the 38th Infantry Division seal the entrance to a Japanese-held cave with high explosives. The inhabitants were trapped inside and suffocated.

“None of us would leave our holes to help him,” Raphael said. “Anything moving in the pitch black night would be shot or get a grenade thrown at him.” In the morning, the soldier died. Rather than remove his potentially booby-trapped body, the soldiers endured the odor in the 100-degree temperature as maggots consumed the corpse.

The Japanese were finished as an effective fighting force. As the month wore on, the Americans’ mission became one of supporting the Fil-Americans, who were assigned the lead role in tracking down the remaining stragglers —thousands of whom would share a fate similar to that of the soldier on Mount Ayaas and never be accounted for.

It had been a long campaign, but it might have been even longer without the use of new tactics—such as using antiaircraft lights against low-lying clouds to illuminate enemy lines while keeping one’s own troops in shadow—and new technology such as napalm, recoilless rifles, flamethrower tanks and, toward the end, helicopters. Carrying two wounded at a time, the choppers eliminated long, arduous handcarries and would save many lives in future battles.

When faced with steep cliffs or heavy rains, however, the Americans took a page out of ancient history and devised bamboo ladders or catapults, or relied on carriers and carabao (water buffalo), whose finicky ways forced Army engineers to interrupt their road building to bulldoze mud wallows. Like so many campaigns in World War II, the battle against the Shimbu Line combined advanced technology, planning, and logistics with seat-of-the-pants improvisation.

At a time when Nazi Germany was in its death throes and a ferocious battle was raging on Okinawa, the fragmented actions against the Shimbu Line had little impact on America’s consciousness. But, in regard to the Luzon campaign as a whole, Smith says, “It is doubtful that any other campaign of the war had a higher non-battle casualty rate among American forces.”

An enervating climate, a host of diseases, unbroken service of up to three years for many soldiers, and a chronic shortage of troops combined to make the battle a grim, exhausting experience. When, on July 1, control of Luzon operations was passed to the Eighth Army, there was little celebration—particularly for the men of the 43rd and 1st Cavalry Divisions, who remained with the Sixth Army to prepare for Operation Olympic, the invasion of the Japanese home island of Kyushu, planned for November 1945.

As these battle-weary men entered camp near Cabanatuan—where the veterans of Bataan had so recently been liberated—they had no idea that their fighting days were over.

David Lashway is a proofreader who lives in Chicago. His research into the Ipo Dam campaign was inspired by the experiences of his late father, a soldier of the 169th RCT.

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