As it had for centuries, the thrust of military engineering during World War II focused essentially on breaching and building. Combat engineers engaged in a variety of offensive tasks, such as conducting river-crossing operations, breaching minefields, and countering other enemy defensive measures. They also provided defensive support to combat elements by employing minefields and other obstacles to hamper or channel enemy troop movements; on occasion, they performed the secondary mission of fighting as infantry. Construction engineers were involved in larger and more permanent projects—roads, railroads, airfields, pipelines, depots, camps, training facilities, and other works designed to sustain their nations' war efforts at home and elsewhere.
For the most part, all nations recruited their military engineers from the experienced civilian sector whenever possible, but they also counted heavily on induction pools, after which active military engineers trained inductees to needed skill levels. The efforts of the military engineers of belligerent nations other than the United States were considerable, and those engineers also played key roles in supporting their nations' war aims and fighting forces. However, their activities were on a much smaller scale, in terms of both volume and geographic setting, compared with those of U.S. military engineers. In this effort, the U.S. Army Corps of Engineers was the most important. It conducted operations on a worldwide stage from the Arctic to the Tropics, in terrain that included jungles, deserts, and mountains.
The Allied Powers
In mid-1939, when Adolf Hitler was pressing his territorial demands in central Europe and the Japanese were already at war in China, the U.S. Army Corps of Engineers had about 800 officers and 6,000 enlisted men in active service, with eight to nine combat engineer regiments, two engineer squadrons, and a topographic battalion staffed at some 70 percent of authorized strength. During the 1920s and 1930s engineer officers spent most of their time involved in the branch's civil works program in districts that were aligned geographically with the nation's major watersheds. Regular Army engineer officers were limited in their troop experience, but for those in the corps, the large civil works projects and contract construction experiences would stand them and the army in good stead in planning for and meeting the engineering and construction demands during mobilization and the succeeding war years. To support amphibious operations in the war, the army formed six engineer amphibious brigades. Three served in the Pacific, and three operated in Europe (two of these brigades later participated in the invasion of Okinawa in the Pacific). By spring 1945, the engineers numbered more than 500,000 officers and enlisted men, comprising 8 percent of U.S. Army strength.
In January 1941, the Corps of Engineers undertook, in addition to ongoing civil works missions, all construction for the army's war effort, including military as well as industrial projects. The corps oversaw "construction of a wide range of factories, most notably for aircraft and tank assembly and the production of ammunition. Military installations included camps for 3.5 million soldiers, depots, training facilities, ports, and the Pentagon. All told, the wartime mobilization program involved more than 27,000 projects and cost $15.3 billion" (U.S. Army Corps of Engineers, 1998.) Perhaps the crown jewel endeavor for the Corps was the manhattan Project, under the leadership of Brigadier General Leslie R. Groves.
By the summer of 1941, large naval bases were under construction at Guam, Midway, Wake, Pearl Harbor, Iceland, Newfoundland, Bermuda, Trinidad, and many other places, carried out by civilian contractors under the engineering supervision of the Navy's Bureau of Yards and Docks. Following the Japanese attack on Pearl Harbor, it became impractical to use civilian labor in war zones and there was a need for a militarized naval construction force to build advance bases in the war zone. This situation resulted in the establishment of the Seabees (whose name was derived from the acronym for "construction battalions," CB).
The Seabees quickly made their mark, particularly in the Pacific Theater but also in the Atlantic Theater of Operations. They constructed over 400 advanced bases along five strategically important routes beginning in the continental United States. The South Atlantic route went through the Caribbean Sea to Africa, Sicily, and up the Italian peninsula; the North Atlantic route went through Newfoundland to Iceland, Great Britain, France, and Germany; the North Pacific route went through Alaska and along the Aleutian Island chain; the Central Pacific route went through the Hawaiian, Marshall, Gilbert, Mariana, and Ryukyu Islands; and the South Pacific route went through the South Sea islands to Samoa, the Solomons, New Guinea, and the Philippines. All the Pacific routes converged on the final destination of the Japanese home islands.
The standard Seabee unit was the construction battalion, but special units were formed, such as stevedores and longshoremen as well as maintenance, dredging, trucking, and pontoon assembly. At war's end, the Seabees were organized into 151 regular construction battalions, 39 special construction battalions, 164 construction battalion detachments, 136 construction battalion maintenance units, 5 pontoon assembly detachments, 54 regiments, 12 brigades, and, under various designations, 5 naval construction forces.
In recognition of airpower's impact on modern warfare, the Army Corps of Engineers developed the concept of an engineer aviation regiment to construct airfields that would be needed for any foreign deployment by the army air forces. By the time the war was over, engineer aviation units had built untold numbers of airfields in every theater. Critical to this effort was airfield construction throughout the United States. By mid-1943, the corps had completed some 1,100 domestic military and civil airfield projects. Between 1940 and 1941, engineer aviation units, as well as corps districts, were involved in construction in Newfoundland, Greenland, Iceland, Bermuda, and the Azores (the North Atlantic Air Routes) that provided the means to ferry aircraft to Britain. The South Atlantic Air Route from Miami, Florida, to the Middle East utilized airfields in the Caribbean, Brazil, and Africa. It began operations in September 1941, and following the U.S. entry into the war, it became the preferred all-weather route to theaters of operation in the Mediterranean, eastern Europe, and Asia.
Beginning in 1941 in the Middle East, British and U.S. Army engineers constructed a road and rail supply line to the Soviet Union through Iran, including port expansion in the Persian Gulf. This supply route, which provided a steady flow of Lend-Lease aid, was instrumental in the Soviet Union's victory on the Eastern Front. Soviet engineers were masters of minefield operations and accomplished all the usual combat engineer tasks. For example, they built corduroy roads as alternate means to support frontline troops along the Stalin Line.
In the Allied invasion of Normandy, France saw the result of imaginative Allied planning in the construction, principally by U.S. and British engineers, of Mulberries (artificial harbors) together with bombardons and phoenixes (floating steel and concrete caissons); there were also pier heads—platforms that raised and lowered mechanically with the tide and provided still-water conditions around the clock, enabling supplies and equipment to be moved across the beach to support the advancing troops in the absence of available ports. U.S., British, and Canadian engineers in the initial assault waves cleared routes through minefields and fought as infantry to secure avenues of advance through the German positions overlooking the beaches. As combat moved inland, Allied engineers rehabilitated damaged port facilities, such as that at Le Havre, and repaired the railroads as well as the roads and bridges to enable supplies to move from other French and Belgian ports to the front.
In the Pacific, U.S. Army and Canadian engineers built the 1,450-mile Alaska-Canada (ALCAN) Highway, which went through British Columbia and the Yukon Territory to Alaska as a counter to potential Japanese control of the North Pacific; it was completed in November 1942. The airplane played a vital role in the Pacific campaigns, where existing facilities were few, and engineers carved airfields out of jungle and coral. In the Mariana Islands, for example, they provided bases for the Boeing B-29 Superfortress bombers to conduct the strategic bombing of the Japanese home islands and drop the atomic bombs on Hiroshima and Nagasaki. The U.S. Pacific strategy called for an abundance of facilities (in addition to airfields) that did not exist, such as ports, huge logistical depots, camps, and roads. American engineers, both army and navy, provided the needed military infrastructure that the island-hopping Pacific campaigns demanded. The engineering effort was so important that Southwest Pacific Theater commander General Douglas MacArthur, himself a serving engineer officer for many years, referred to the fighting in his theater as an engineer's war.
In the China-Burma-India Theater, the Burma (Ledo) Road was another joint Allied engineering project. After the Japanese capture of Rangoon in March 1942 cut off the last Allied land route to China, the British and Americans developed a plan to build a new resupply route from Assam, India, across northern Burma to a junction with the old Burma Road. U.S. Army engineers, together with Chinese and Indian labor, began construction in December 1942, crossing 430 miles of jungle, mountains, and rivers. The road was formally completed on 20 May 1945, the longest invasion pipeline ever built.
Not to be overlooked, the U.S. Corps of Engineers' long-standing civil works responsibility to develop, operate, and maintain the inland waterway system played a key role in the war effort within the United States. Barge traffic carried petroleum products and other strategic materials. The improved waterways of the Mississippi system provided a highway for thousands of vessels, including the destroyer escorts, submarines, frigates, minesweepers, landing craft, and small cargo vessels that would be built at inland shipyards, thus enabling the large coastal shipyards to focus on building the larger combatant and merchant vessels.
The Axis Powers
Germany's march to war saw the formation of the Todt Organization in 1933, named for its head, Fritz Todt. Initially, the organization constructed the Third Reich's autobahn road system and provided the German army with engineers and construction specialists to support the country's war aims. In 1938, it worked on Germany's West Wall (Siegfried Line) defenses, designed to hold back any French army attack so that Germany could concentrate its military resources in the east against Poland.
Among its World War II missions, the Todt Organization built and repaired bridges, railroads, dams, airfields, and fortifications, as well as factories. It had charge of exploiting the minerals of the Balkans region and shipping them to the Reich, and it assumed responsibility for the reconstruction and maintenance of the Soviet Union's transportation network. The Todt Organization made use of vast numbers of conscript laborers throughout German-occupied Europe, mobilizing almost 1.5 million persons, 80 percent of whom were non-Germans and many of whom were prisoners of war (POWs). The organization's most ambitious task was constructing, together with German army engineer troops, the Atlantic West Wall from Norway to the Bay of Biscay, which constituted the German defenses designed to prevent the Allied invasion of France.
Engineer troops were key elements in the German army's planning for the invasion of Poland, as well as Germany's other earlier blitzkrieg campaigns. They were organized into infantry-engineer assault teams in the attacking divisions. German pontoon bridge units and sappers were especially active in offensive operations. Special engineer staffs were established at the army and army group levels to provide technical direction for bridging and other engineer work, including placing captured rail lines back in operation. Defensively, the Germans used extensive minefields in the fighting in North Africa as well as on the Eastern and Western Fronts, and German sappers were on point in clearing minefields during offensive operations. Typical of German engineering's defensive design prowess, the Normandy beaches provided an imposing array of multiple belts of obstacles (including millions of mines) that were covered at high tide and exposed at low tide, as well as extensive minefields inland.
Italian military engineering played a vital role in that nation's invasion of Ethiopia, moving men, equipment, and supplies across very difficult terrain. Japan also employed military engineers extensively. Japanese expansion brought about airfield construction and the heavy fortification of occupied areas, and airfields and naval base facilities on Formosa, Truk, and Rabaul were important in supporting Japanese island operations elsewhere in the Pacific. Japanese engineers were also very active in defensive operations in the Pacific islands. In addition to constructing beach obstacles, they designed blockhouses, pillboxes, and other defensive works. They utilized reinforced concrete, coral, coconut logs, caves, and tunnels dug into volcanic formations with great effectiveness against bombing, naval gunfire, and infantry assaults conducted by invading Allied forces in the Marshall, Gilbert, and Solomon Islands, as well as at Okinawa and Iwo Jima. The Japanese frequently used forced labor and prisoners of war in their engineer/construction efforts.
Japan's principal supply route to its armies in Burma was the railway across the Dawna Range from Thailand to Burma. In a vast construction effort, the Japanese army employed thousands of Allied POWs and local nationals. A large number of the workers died when they were forced to hack a path through the jungle, utilizing the most primitive of tools and working with little food and virtually no medical care.
Military engineering was a vital component of the war effort on both sides. Without doubt, engineering operations, particularly those of the United States, played an important role in the Allied victory in the war. C. Ernest Edgar III
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C. Ernest Edgar III