One thing I like about Harry is he is more than willing to devote attention to significant, but lesser-known issues. The jungles of the Pacific are justifiably associated with infantry actions, but the tanks played no small role either. Anyway, I am pleased to hand over the keyboard to him for this two-parter. - The Chieftain
Article by Harry Yeide
The US Army did not have a doctrine for using tanks in jungles when it entered the war. If someone had told the masters of doctrine at Fort Knox that somebody was going to, they probably would have just laughed. The 192d and 194th Tank battalions sometimes fought in jungle conditions during the futile defense of the Philippines after the Japanese invasion in December 1941, but Luzon’s looked more like Europe’s than did many islands in the Southwest Pacific. Luzon, for example, had roads. Only the US Marine Corps employed tanks on Guadalcanal, so the army learned nothing from the battle that would help it use tanks on the next jungle-clad island on which the Americans would have to fight the Japanese: Bougainville in the Solomons.
The 3d Marine Division on 1 October 1943 had landed on the west coast of Bougainville. In November, the 37th Infantry Division joined the Marines. The 754th Tank Battalion arrived on 6 January 1944, and the Americal Division, with which the tankers had partnered while training on New Caledonia, disembarked a week later. The tank battalion was subordinated to XIV Corps rather than either of the infantry divisions, and initially it deployed to secure the perimeter at Empress Augusta Bay as corps reserve.
Soldiers on the scene were going to have to come up with a way to use tanks with the infantry on the fly, largely through trial and error. Planners at XIV Corps drew on lessons learned during tank-infantry training conducted on Guadalcanal before the operation and had gathered what information they could on the prior use of tanks to support infantry in the Pacific. They implemented a training program for the tank-infantry-engineer teams the corps intended to use in Bougainville’s rain-soaked jungles. “This [combat] experience has been limited both in number of times tanks have been used and in number of tanks used in any one attack,” the corps noted in a training memorandum issued on 20 January. “Therefore, the principles enumerated cannot be considered as final.”
Some of the concepts taught on Bougainville were old-hat, such as using tanks only on appropriate terrain. Others were novel. “In the jungle, the firepower of the tank assumes far greater importance due to the inherent limitations of maneuver and shock action. Therefore a portion of the tanks must be formed in line in order to exploit maximum firepower.” Combat experience had shown that 37mm canister rounds and machine guns could clear jungle growth to reveal pillbox openings. High-explosive rounds and flamethrowers could then be fired through the opening or, failing that, armor-piercing rounds often created a hole big enough for HE fire.
Formations had to be extremely simple to permit any control, and tanks were to be pre-positioned behind the line of departure. Advances had to be short and by bounds with frequent halts for reorganization and reorientation.
The corps mandated that tanks be used en masse, at least one company at a time. This notion doubtless reflected the hand of some unrecorded armored officer, trained in Fort Knox notions of tank warfare, and it was so inapplicable in the jungle that it was among the first to be ditched in practice. Planners said the infantry had to protect the tanks during approach, attack, and withdrawal, and the tanks had to support the “doughboys,” as tankers called the infantry, by fire. This insight was the heart of armored warfare in the jungle.
Training emphasized that the infantry and tanks maintain constant communication, but the means were primitive. The armor and the infantry commanders were to establish a radio link at the tank company-infantry battalion level (only possible if the tankers loaned a radio to the doughboys). At the tank platoon level, a sound-powered or field telephone was to be run between each tank and the local infantry commander by taping the phone wire to a light cable towed by the tank.
Engineers were crucial to the team to help tanks overcome terrain obstacles, such as by using bulldozers to clear paths or by bridging streams. In cases where mutually supporting pillboxes could be bypassed, small engineer-tank-infantry teams were to destroy them.
The tankers saw their first action on 30 January with the Americal Division’s 132d Infantry, before any of the new training could take place. The operation featured massed use of armor—twenty light tanks—to support the GIs. The regiment’s journal indicates that the tanks advanced some 200 yards beyond the perimeter, stopped, and shelled Japanese positions, accounting for eleven pillboxes. A Japanese 90mm gun destroyed one tank, and a second bogged down and was abandoned. At least on one flank, a squad of infantry provided effective cover for a platoon of tanks.
The infantry and tankers had undergone XIV Corps’ training regimen and received their allotment of Sherman tanks by early March, when the Japanese Seventeenth Army launched a desperate and ultimately pointless counterattack to eliminate the XIV Corps lodgment, which was only 8,000 yards deep. The Japanese confronted a daunting objective, for the American line consisted of fortified pillboxes and firing positions, protected by barbed wire and minefields. The first serious Japanese attacks hit before dawn on 9 March. On 12 March, elements of the Japanese 45th Infantry Division attacked the 37th Division’s 129th Infantry on a narrow front. The American regiment held a stretch of low ground in the center of the division line, where the Japanese established a salient 200 yards deep and 100 yards wide into the 2d Battalion’s line. The Japanese drove the GIs out of seven pillboxes, and efforts to retake the ground recovered only two pillboxes.
The next morning, the Japanese attacked again and grabbed another pillbox. At 0945 hours, the 1st Platoon, Company C, 754th Tank Battalion, which consisted of three Shermans and two light tanks, arrived to support a counterattack using the new tactics. Major General Oscar Griswold, XIV Corps commanding general, had released the tanks with the stipulation that they be used in an attack rather than defense. The tanks moved out as expected, but the infantry failed to stay close or to designate targets, and the sally broke down. The tanks had difficulty firing at the Japanese, who were hunkered down in ravines with steep slopes. The team tried again at 1315 hours, and again the infantry failed to stick close. Japanese infantry surrounded two tanks for a few nail-biting minutes but were driven off.
The 2d Platoon—also consisting of three medium and two light tanks—arrived to relieve the 1st Platoon, and at 1700 hours, the team made its third attempt. This time, the infantry stuck close to the tanks and designated targets by telephone and colored smoke. The tanks approached within fifteen yards of the Japanese positions and hit them with 75mm and machine-gun fire. One 75mm round killed eighteen enemy soldiers sheltering in the roots of a Banyan tree. The combined assault reclaimed the former line with hardly any losses among the doughboys.
The Japanese on 15 March again penetrated the line in the 2d Battalion’s sector and seized a pillbox. A counterattack supported by the 2d Platoon’s tanks failed because even infantry NCOs riding in the tanks could not distinguish between the pillboxes held by friend and foe. The tanks fired at visible targets from a distance, but the Japanese had moved in heavy weapons and held firm.
The tank-infantry team tried again at 1635 hours. “Coordination between infantry and tanks was good,” a corps report related, “until several telephones were shot away. Although infantry accompanied the tanks, close-in protection was not continuous, and the enemy succeeding in exploding two mines on the tanks. . . . At one point, a group of enemy swarmed onto one of the assault tanks; several well-placed charges of canister from the support tanks swept them away without damage to the assault tanks. When the fierce fighting ended at dark, our forces had completely annihilated the enemy.” One hundred ninety Japanese dead were counted within the original American line.
The whole cycle repeated itself on 17 March. In the American counterattack, “ideal coordination between the tank platoon and its supporting infantry platoon was realized,” XIV Corps reported. “Infantry squad leaders could see the fresh dirt which indicated enemy entrenchments, halted the tanks just short of these, tossed out colored smoke grenades, and gave directions for fire. 75mm and 37mm shells blew the enemy from the ground. Jap machine guns delivered a stream of fire against the tanks but inflicted no damage. Infantry quickly spotted the gun positions, some of which were only fifteen yards off on the flank. These were designated as targets to the tanks and were quickly knocked out. By 0950, our [main line of resistance] was restored, and 200 enemy dead were counted within our wire.” (The 754th, like most battalions in the Pacific theater, put rubber block or rubber chevron tracks on the tanks. These proved better than steel chevron tracks for gripping mud.)
On 4 April, after having tested its ideas in combat, XIV Corps issued a memorandum that concluded most of its doctrine had proved sound. It had nevertheless refined its model attack formation. The new infantry-tank-engineer team consisted of one “platoon” of tanks (in fact an ad hoc platoon consisting of three medium and three light tanks), a platoon of infantry, and a few attached engineers. Three medium tanks led the assault spread across a frontage of fifty yards. Their mission was to advance slowly, firing cannons and machine guns to drive the enemy to cover and to strip camouflage from pillboxes. A second echelon of two light tanks followed by twenty-five yards, each behind a medium tank on one flank. The light tank could fire the extremely useful canister round, which the medium tank could not. Their mission was to knock out bypassed pillboxes, shoot snipers from treetops, and to protect the medium tanks using machine guns and canister fire from attack by foot troops carrying magnetic mines or charges. Two GIs acting as target designators, a telephone orderly from the tank battalion attached to the squad leader and talking to the tank crew through a field telephone, a squad of riflemen and BAR men, and a few engineers with demolitions and flamethrowers walked immediately behind in a wedge formation to avoid canalization in the tracks of the tanks. The designators showed the tankers what to shoot, while the others rooted out enemy infantry and protected the tanks from close infantry assault. The platoon reserve and a third light tank came last. An entire infantry company could be arrayed with three such formations side by side.
The target designators were an effective invention. “Tanks proved to be almost blind in thick jungle,” the corps noted. Tracer fire proved inadequate for designating targets such as well-hidden pillboxes. A red or violet smoke grenade only obscured the target. Trial and error showed that if the grenade’s fuse was unscrewed and half the charge removed, the level of smoke was just right. Target designators either tossed the modified grenades by hand or fired rifle grenades at longer ranges.
In a jungle advance, tanks could operate for about three hours before needing reservicing. Typically, the tanks could conduct two such sorties during the day. The pace of jungle combat—tanks advanced in first gear for only twenty-five to seventy-five yards before stopping—was tough on the engines and could result in vapor lock.
Communication plans had fallen short of needs. Only one fix had worked under fire on Bougainville: Placing an EE-8 field telephone inside the each tank’s turret, and running a wire to a handset mounted on the rear of the tank. The soldiers had learned that if the box itself were strapped outside the tank, enemy fire would damage it. The telephone orderly from the tank battalion, armed only with a pistol, could translate the wished of each infantry squad leader into words the tank crew would understand.
37th Infantry Division GIs on Bougainville advance behind a Sherman belonging to the 754th Tank Battalion on 16 March 1944. They are using a formation developed on the island for jungle warfare, with target designators at the rear corners of the Sherman and riflemen, BAR men, and engineers in a wedge behind. (Signal Corps photo)
In small-island jungle-type warfare, the relation of tanks and infantry should be comparable to that of Siamese twins.
Lt. Col. W. M. Rodgers, 710th Tank Battalion
See my website: World War II History by Harry Yeide
See the book from which this article derives: The Infantry's Armor
 “The Tank Infantry Engineer Team in Jungle Operations,” memorandum, Headquarters, XIV Corps, 20 January 1944.
 “Combined Infantry-Tank-Engineer Operations in the Jungle,” memorandum, Headquarters XIV Corps, 4 April 1944. John Miller, Cartwheel: The Reduction of Rabaul: United States Army In World War II, The War in the Pacific (Washington, D.C.: Office of the Chief of Military History, Department of the Army, 1959), 351ff.
 “Questions on Operation of All Types of Military Vehicles in Mud—Ordnance Technical Letter #24.”
 “Combined Infantry-Tank-Engineer Operations in the Jungle,” memorandum, Headquarters XIV Corps, 4 April 1944. Combat Lessons Number 2, War Department, nd, 62.
 New Guinea, the U.S. Army Campaigns of World War II Series (Washington, D.C.: Center of Military History, n.d., online reprint of CMH Pub 72-9, http://www.army.mil/cmh-pg/brochures/new-guinea/ng.htm, as of February 2008), 1-9.
 M. Hamlin Cannon, Leyte: The Return to the Philippines: The United States Army in World War II, The War in the Pacific (Washington, DC: U.S. Army Center of Military History, 1993), 3. (Hereafter Cannon.)
 “The Battle of Lone Tree Hill,” manuscript, records of the 20th Infantry Regiment. AAR, 6th Cavalry Reconnaissance Troop. Mauer, et al, 5-10. Martin. Hallanan, 45. Robert Ross Smith, The Approach to the Philippines: The United States Army in World War II, The War in the Pacific (Washington, DC: Office of the Chief of Military History, Department of the Army, 1996), 252ff.
 “Requirements of Tank Design and Operation in Relation to Effectiveness of Armored Personnel,” Pacific Warfare Board Report No. 60, 9 September 1945, NARA, RG 407, Special File, 4-7.60/45, box 24464. (Hereafter “Requirements of the Tank Design and Operation in Relation to Effectiveness of Armored Personnel.”)