Photograph of engineers constructing a runway
U.S. Army. Via Leighton and Coakley (1955)

Engineers were troops trained in the construction and demolition of military installations.

Those engineers who specialized in destroying enemy fortifications under fire were known as combat engineers. They were given infantry training and were typically equipped with special equipment such as explosive charges, flamethrowers, and mine detection and removal gear. A battalion of combat engineers was typically included in the table of organization of combat divisions.

Non-combat engineers were responsible for construction of roads, airfields, port facilities, and anything else required to support military operations. Because of the primitive conditions in most of the Pacific theater, almost the entire military infrastructure had to be constructed from scratch. This was a labor-intensive process even for the best-equipped armies, and large numbers of service troops (unskilled or semi-skilled laborers working under the direction of engineering officers) were employed in the Pacific.

Japanese Engineers

A Japanese division included an engineer regiment which normally consisting of three companies and a material platoon, numbering about 900 to 1000 men. A few second-line divisions were limited to engineer regiments of two companies numbering about 240 men and 20 horses. Nondivisional engineer regiments resembled division engineer regiments in strength and organization, but were classified by function: "A" for open warfare, "B" for positional warfare, "C" for heavy bridge building, "D" for landing operations, "E" for river crossing and "F" for attacking pillboxes and other fortifications.

Yamamoto Isoroku was aware of the critical role engineers would play in any Pacific campaign (quoted in Evans and Peattie 1997):

As I see it, naval operations in the future will consist of capturing an island, then building an airfield in as short a time as possible— within a week or so — moving up air units, and using them to gain air and surface control over the next stretch of ocean.

However, Japanese engineering resources proved tragically inadequate when war came. Engineering machinery, such as bulldozers, were almost completely lacking. Because of the shortage of heavy equipment, Japanese engineer units tended to include a sizable number of labor troops, usually Koreans, who occupied the bottom rung of the Japanese Army social hierarchy. Many of the "Japanese soldiers" captured in the early Allied offensives were, in fact, Korean laborers who were unimpressed with the Bushido code. In addition, it has been alleged that burakumin were largely used as labor troops. Manpower and hardihood was substituted for machinery with such techniques as having engineers stand in stream beds holding planks on their shoulders for assault troops to cross.

Beginning in November 1941, the Japanese Navy organized setsueitai ("construction units") composed mostly of Korean or Taiwanese semiskilled laborers led by Japanese officers and Japanese civilian overseers. These units never achieved more than a fraction of the capability of the U.S. Navy Seabees, but the failure of Japanese commanders to understand their limitations meant that they were often expected to do the impossible. They were supplemented by unskilled labor battalions during construction work and often were incorporated into konkyochitai ("base forces") for last-ditch defense.

During the Centrifugal Offensive, Japanese engineers were mostly employed in repairing captured Allied ports and airfields, a task within their capabilities. However, as the Japanese offensive moved into the undeveloped reaches of the Pacific, their construction units were faced with building facilities from scratch. Such work proceeded at a glacial pace compared with the Americans.

Notwithstanding their limitations, Japanese engineers proved adept at constructing formidable bunkers from local materials. These typically consisted of coconut logs held together with iron supports and topped with more coconut logs and earth. Where time and materials permitted, bunkers were constructed of reinforced concrete, as was the case with the larger bunkers at Tarawa.

American Engineers

An American division included an engineer battalion of 647 men. Nondivisional engineer battalions were often specialized for particular tasks. For example, aviation engineer battalions numbered 27 officers and 761 men with 146 vehicles of all types.

American engineers were highly professional but never available in the numbers the commanders would have liked. However, technology such as Marston mats was developed that could be used to construct airstrips and roads using unskilled labor, and heavy equipment such as bulldozers was provided much more generously for American engineers than their Japanese counterparts.

In an ironic parallel, black Americans were employed by the U.S. Army in much the way that Koreans and burakumin were employed in the Japanese Army. Blacks saw almost no combat in the Pacific except as mess attendants on Navy ships. The Marines steadfastly refused to accept black American volunteers until 1944, and the only black Army division in the Pacific saw virtually no combat duty. Black troops were used extensively by engineers as laborers, though they were supplied with better equipment and enjoyed substantially better working and living conditions than Korean laborers in the Japanese Army.

The U.S. Navy developed its own engineering corps, the Naval Construction Battalions or Seabees, which developed airfields and port facilities in captured territory. Marine divisions briefly included an engineer regiment that provided a common command echelon for the division's pioneer and engineering battalions plus an attached Naval Construction Battalion. Later the Navy pulled the Seabee battalions out of Marine divisions, and the Marine engineer regiments were dissolved, their remaining battalions again being attached directly to the division headquarters.

Marine pioneer battalions were assigned, one per division, to provide manpower for shore parties without detracting from the fighting strength of the divisions. These shore parties were supplemented by Marine replacement drafts and Navy stevedore battalions. The shore parties were commanded by senior logistical officers, initially a Marine shore party commander with a Navy beachmaster as assistant. Later, as Army divisions were incorporated into landing forces, the shore party groups were tailored for each landing.


Evans and Peattie (1997)

"Handbook of Japanese Military Forces" (1944-9-15)

Harmsen (2013)

Rottman (2002)

Spector (1985)

Tillman (2010)

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