The Corps of Engineers: The War Against Germany
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Chapter 1: Introduction
On the eve of American involvement in World War II, the U.S. Army Corps of Engineers had 150 years of experience in national wars and in statutory assignment to civil works projects outside the Army. Its veteran officers could hark back to an unprecedented performance in World War I, when the Corps had expanded from 2,454 officers and enlisted men to nearly 300,000174,000 in France alone when the Armistice was signed.1
In unexpected measure their works on the Continent from 1917 to 1919 enlarged upon traditional engineer functions, especially as they applied to facilitating troop movement. In several ports where the French government turned over wharfage to incoming American forces, the 17th and 18th Engineer Regiments, two of the first nine engineer regiments to arrive, constructed additions to docks, erected depots, and then laid new rail lines linking the facilities to the French national system and the Zone of the Advance that included the front line itself. An entire regiment spent the war in forestry operations, providing much of the lumber for rail ties, housing, and hospitals for the American Expeditionary Forces. In forward areas engineers braved the same fire as the infantry to build narrow-gauge rail nets for supply and troop movement, to dig complex trench systems, to string wire, to install bridging, and even to engage the enemy. Engineer flash- and sound-ranging equipment helped direct counterbattery artillery fire. Chemical engineers, the forerunners of an independent postwar Chemical Corps, released gas employed against the Germans in the trenches and developed protective devices and procedures against enemy gas attacks. Elaborate camouflage screens and nets manufactured and painted with the help of French labor masked American equipment and concealed preparations for forthcoming operations.
Falling within the usual definitions of engineer work in war, these activities covered a far wider technical range than ever before in American military engineering experience. So complex and extensive had the operations become, in fact, that one regimental commander declared that the military engineer had died and his close relative, the civil engineer, had taken his
place.2 For all their accomplishments in forging smooth lines of communications from the rear to the front and in providing invaluable services between, the engineers fought in a war distinguished by the lack of forward movement of the front itself until the final months of the conflict.
Events in Europe in the spring of 1940 effectively demonstrated that harnessing the internal combustion engine to new tactics gave much more range and speed to military operations.3 The German defeat of France in six weeks and the narrow escape of the British Expeditionary Force at Dunkirk proved the superiority of the Wehrmacht. Coordinated with aerial attacks that destroyed ground obstacles and threw enemy rear areas into confusion, massed armor assaults on narrow fronts offered the antidote to static trench warfare and allowed rapid decision on the battlefield.
German success with these tactics and the subsequent bombing campaign against Great Britain converted a fitful American rearmament into a real mobilization. Congress appropriated more funds for national defense than the Army could readily absorb with its limited plans to defend the western hemisphere from Axis infiltration or overt military advances in 1940. Like the rest of the Army under this largesse, the engineers accelerated their recovery from twenty years of impoverishment. Though the Corps had been heavily committed to civil works through the two preceding decades, its separate military units were few and scattered across the continental United States and its overseas possessions. Given time to develop additional combat and support units along older organizational lines, the engineers could expand as they had in World War I and take up again their recognized general functions of bridge, rail, and road construction or maintenance; port rehabilitation; and more specialized work in camouflage, water supply, map production, mine warfare, forestry, and the administrative work necessary to support combat forces. But even if engineer elements remained divided into general and special units, the engineers could not simply reactivate old units under this framework in anticipation of a new conflict. The modern method of war generated new missions and demanded new organizational structures, new units, and new types of equipment to accommodate the revolution in tactics.
A reorganization of the Army was already under way.4 Field testing of revisions in the basic organization of the infantry division began in 1937 with a reduction of infantry regiments from four to three to create a flexible and more easily maneuvered force. The organic engineer unit in the smaller division was a battalion rather than an engineer combat regiment. Numerical strength varied in the experiments, but three companies became the eventual standard for engineer battalions assigned to infantry divisions. Responding
to events in Europe in 1940, the Army also developed two armored divisions from its small, scattered and experimental, mechanized and armored elements and provided each division with an organic engineer battalion, eventually numbering 712 men. In imitation of the German organization for panzer divisions, the American engineer armored unit had four companies, one a bridge company equipped with a large variety of military bridging. A reconnaissance platoon of the battalion’s headquarters company was to scout ahead of the advancing division to determine the need for bridge and demolition work or the best detours around obstacles.
Engineer regiments, either for general service or for combat support, survived as separate entities attached to field armies or to corps headquarters. Consisting of two battalions and various supporting companies, these larger units assumed many of the rear-area tasks formerly left to divisional units. The more heavily equipped general service regiment was to perform general construction, maintenance, or bridge work on main routes of communications, and military construction once the engineers assumed that responsibility from the Quartermaster Corps. The combat regiment, with twenty-four machine guns in its normal equipment, was more heavily armed for work in the combat zone but had less heavy machinery than the general service regiment. It was particularly suited to support divisional units in forward areas and had a special role in large-scale assault river crossings.5
Experiments produced new equipment for the revised engineer organizations. In the search for easily transported and rapidly emplaced bridging, the armored force engineers copied the German inflatable ponton system and produced a 25-ton ponton treadway bridge for tanks. Other tests showed the British-designed Bailey bridge to be lighter and more adaptable to a war of movement than the standard American H-10 and H-20 girder bridges. Repeated experience with construction equipment convinced the engineers of the value of heavier and larger bulldozers, scrapers, cranes, and trucks, though the conflicting demands of the American industrial mobilization often made these items hard to procure in the desired quantities. As a result, an engineer unit Table of Organization and Equipment (TOE) immediately before American entry into the war called for much less heavy equipment than eventually proved necessary. Demands for additional heavy equipment of new design arose as the engineers encountered conditions that overtaxed the standard machinery they brought with them to the theaters of war. A new battery-operated magnetic mine detector enabled the engineers rapidly to unearth mines that impeded the advance of friendly troops, but there was little advance intelligence on the nature of Axis mines or the doctrine governing German mine warfare. Engineer map production techniques improved remarkably with the use of aerial photography employing specialized multi-lens cameras and multiplex interpretation systems.
Given the heavy use of tactical aviation and the then-current theories of bombardment aviation, the engineers
also expected to support the Army Air Forces in any future conflict. Established immediately after the spring maneuvers of 1940, the engineer aviation regiment (66 officers and 2,200 enlisted men) consisted of three battalions that could be employed independently. Within two years of its inception, the unit had the highly specialized mission of constructing large rear-area bomber bases and hasty forward fields for tactical aircraft. The regiment carried with it all the necessary earth-moving, paving, and construction machinery and was adequately armed to thwart an enemy airborne attack on the installation under construction. The unit used another idea from abroad—long, narrow steel plank sections, perforated to reduce their weight and linked together to form temporary runways on poor or unstable soil.
The motorization and mechanization of modern armies and the addition of aerial components dictated increased consumption of gasoline and oil in future operations. The engineers met this likelihood with another innovation that eventually proved its value in the theaters of war in North Africa and Europe. The Quartermaster Corps had distributed petroleum products in containers transported to using troops by rail and truck. Though the engineers did not displace this method entirely, they took over and improved pipelines to lessen the load on vehicles in combat and communications zones. A highly specialized unit, the engineer petroleum distribution company, came into existence to build and operate pipelines from major ports to the immediate rear areas of the field armies.
An engineer role in amphibious warfare was not considered until shortly before the Japanese attack on Pearl Harbor. In all the likely arenas of the obviously approaching war, an advancing army would have to move across expanses of open water. In the Pacific, where the American possessions and the Japanese homeland were islands, the ability to seize objectives depended upon operations across beaches. In Europe, it was apparent by mid-1940 that Axis control of every major port would make similar operations necessary. Though the Army began amphibious training for two infantry divisions in June 1940 and established a research committee to examine possible roles for amphibian engineers, special units for the purpose were still in the future.6
By mid-1941, the Corps of Engineers had embarked upon an ambitious program of revising its military units and equipment. Though not fully ready to fight in an overseas theater, the engineers had done much to adapt to the realities of modern combat and combat support. This process continued as a shadow American staff structure took shape in England.