Photograph of infantry slogging through the mud

U.S. Marine Corps. Via

It has often been observed that, no matter how advanced military technology becomes, it is the individual infantry soldier who claims victory by occupying the objective. This was as true in the Pacific War as in any other.

Traditionally, the infantry were those soldiers who marched on their own feet carrying their own individual small arms and grenades. The infantry's heavy weapons (impedimenta), such as medium and heavy machine guns and mortars, were designed to be broken down for foot transport but could still be burdensome. Usually these weapons were assigned to heavy weapons companies, which sometimes were equipped with pack animals or vehicles to carry their heavy equipment. Infantry on the march could advance at a sustained pace of about 4 miles (6 km) per hour for a total of about 25 miles (40 km) per day. Considerably faster movement was possible for short periods of time.

An infantryman's load varied but could be in excess of 70 pounds (30kg) when beginning a long march with an uncertain supply chain. According to Allen (1984), a Japanese soldier in Burma in 1944 might carry twenty days' rations, four grenades, 300 rifle rounds, a great coat, tent, blanket, canteen, mess kit, gas mask, and entrenching tools. His Chindit enemy was equally burdened with a similar assortment of equipment.

An infantry squad was typically around 12 men and was led by a non-commissioned officer (sergeant or corporal.) Three or more squads were organized into a platoon led by a lieutenant, and three or more platoons were organized into a company led by a captain. Three or more Infantry companies were organized into a battalion led by a major or lieutenant colonel, while three or more Infantry battalions were organized into an infantry regiment led by a colonel. (In the British army, this echelon was the brigade, led by a brigadier, who was not considered a general officer.) Infantry regiments were combined with units from the other branches, primarily artillery but sometimes cavalry and armor, as divisions of various types. In addition, each maneuver formation included supporting elements, such as a mortar section or a bazooka team in a platoon or a heavy weapons company in a battalion. The manpower and equipment of the higher echelons (described by a table of organization and equipment, or TO&E) varied considerably from army to army and even within the same army, with the Japanese army being particularly relaxed towards unit standardization.

The infantry was supported in its operations by the divisional artillery, cavalry, and armor. Sometimes an artillery battery or tank battalion was temporarily attached to an infantry battalion or regiment to provide fire support for a particular operation. In American divisions, such attachment was often semipermanent, particularly since the Americans raised a large number of independent tank battalions that were not assigned to armored divisions. Horse cavalry was almost unheard of by the time war broke out in the Pacific, but divisions usually incorporated scouting units equipped with light armor or other vehicles that filled the traditional scouting and screening role of the cavalry.

Morale. Infantry fighting power in modern warfare came through a combination of morale and tactics. The most important element of morale is unit cohesion, which boils down to the unwillingness of the individual soldier to let down his comrades in combat. It is achieved largely by taking care to train men together who will fight together, by maintaining unit integrity during combat, and by returning wounded or sick men to their original unit. These seemingly simple and obvious principles were ignored by the U.S. Army during the Second World War, at considerable cost in unit cohesion, but were fundamental to both the British and Japanese systems.

The American Army adopted a "scientific management" approach to its personnel policies that was astonishingly inhumane for the armed forces of a great liberal democracy. The goal was to make the individual soldier an interchangeable cog in the military machine. Soldiers who completed basic training were sent individually to wherever they were needed, and often found themselves deployed directly to the front line among strangers. When they recovered from wounds or sickness, they found themselves in a replacement depot from which they might be redeployed to any unit except (it seemed) their original one. Such unit cohesion as existed in the U.S. Army in the Pacific was largely accidental, arising from the long lines of communications and episodic nature of most battles. These circumstances tended to keep units together and provided opportunities for replacements to train with their units before combat. Neither the Marines nor certain specialized Army branches (cavalry and airborne) adopted the Army infantry system, and their morale benefited accordingly.

By contrast, Britain employed the regimental system, in which the regiment was a recruiting and training echelon rather than a combat formation.  Battalions were raised and trained by a regiment, usually from the same geographical area, then deployed as units to combat divisions. When a battalion was worn down by prolonged combat, it was taken off the line as a unit to absorb replacements, and might be redeployed to a different brigade as circumstances required.

The Japanese organization was nominally similar to the American, but units down to company level were recruited geographically and trained together. A division was raised from a large geographical district, while its individual companies might be men from the same small town. This was ideal for building unit cohesion, particularly in a society that was barely a century out of its feudal era. The down side was that a defeat in battle might be devastating to a small geographical area which lost most of its young men. Citizens of a small Japanese fishing village in Gifu Prefecture still make regular pilgrimages to Guadalcanal at the turn of the 21st century to look for remains of relatives recruited into a formation that was annihilated southwest of Henderson Field.

Japanese unit cohesion appears to have been qualitatively different from that of the Western powers. Whereas the armies of the United States and Britain drew most of their unit cohesion from horizontal solidarity -- enlisted men fighting for each other -- the Japanese seem to have drawn much of their unit cohesion from vertical solidarity -- enlisted men fighting for their NCOs and junior officers.

For all its faults, the American system was not adopted without reason. Because all replacements were part of a single theater pool, there was no possibility of a division in heavy combat exhausting its replacement pool while divisions in quiet sectors had an abundance of replacements standing idle. The Army believed that this would allow a division to remain in the line indefinitely, without having to be relieved by a fresh division when its replacement pool was exhausted. However, this also meant that an infantryman could expect to remain in combat until he became a casualty or the fighting ended. Again, this was less severe of a problem in the Pacific than in Europe due to the episodic nature of the fighting. On the other hand, a Pacific infantryman whose unit was not in contact with the enemy had nowhere to go for leave, unless he was lucky enough to find transportation to Australia or New Zealand. This was a very rare occurrence once his unit was deployed to the forward area.

Infantry Tactics. Modern firepower makes frontal assault a suicidal proposition, to be attempted only when there is no alternative. Fire kills. This was already clear by the time war broke out in the Pacific. What was less clear was that modern firepower also made what one might call "frontal defense" an increasingly suicidal proposition. By the time the war ended, it was the case that, if you could see a target, you could hit it; and if you could hit it, you could kill it. Armies were successful when they took advantage of the irregular surface of the Earth to maintain cover -- both in defense and offense -- for as long as possible.

In addition, modern armies depend on a complex web of logistical and other rear area services to maintain their combat effectiveness. Cut a formation off from its rear echelons, and it must either regain contact, surrender, or be crushed. Early in the war, the Japanese proved adept at maneuvering around Allied formations to cut them off from their rear, forcing them to retreat or surrender. The Allies eventually learned to turn the tables on the Japanese by reestablishing communications while isolating the Japanese flanking units. This could lead to the kind of confused lines that developed at Buna, where American and Japanese roadblocks alternated along an important trail for several hundred yards.

The U.S. Army, faced with a massive expansion of its officer corps, taught its citizen-officers a simple tactical doctrine based entirely on the hook. With its divisions triangularized from top to bottom, every maneuver formation consisted of three smaller maneuver formations plus supporting elements. Two of these formations would approach the enemy from the front, drawing his fire and attempting to pin him down with their own firepower. Once fire superiority was achieved, the third formation would maneuver to try to get around the enemy and fall on his flank or rear. This tactic could be applied at all levels, from squad to army group, and it was simple enough to hold up in the fog of battle.

Allied forces also developed an aerial resupply capability that allowed isolated units to continue fighting. In effect, the lines of communication to the rear took the form of a transport bridge passing over the intervening ground. The Japanese never succeeded in developing a comparable capability.

The Japanese excelled at constructing field fortifications. Early in the Pacific, these typically took the form of thick coconut log pillboxes covered in natural vegetation that were exceedingly difficult to spot from a distance. As the war progressed, the Allies became more adept at spotting and destroying fixed beach defenses with air attack and naval gunfire. This led the Japanese to turn to defense in depth, with carefully concealed concrete pillboxes well back from the beach. Such defenses proved deadly effective at Peleliu, Iwo Jima, and Okinawa.


Allen (1984)

Bergerud (1996)

Drea (2009)

Perret (1991)

Van Creveld (1982)

Willmott (1982)

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