During World War II, engineers played multiple roles depending on the situation, and their work included building roads, bridges, ports, airfields and military camps. They were also involved in the construction of petroleum pipelines, warehouses, hospitals, barracks and other such facilities. Combat engineers had to lay mines or clear them as required. They functioned as infantry when needed, supervised the construction of the atomic bomb, maintained vehicles, produced maps, and cleared rubble and other obstructions.
The combat engineers had a primary mission: to keep the army moving and to impede the enemy. With this in mind, they took on necessary work in any situation. They built bridges, sometimes in the dark to avoid drawing the attention of the enemy or under enemy fire at other times. To search for mines, they lay on their stomachs and delicately probed the ground with their bayonets. They engaged in combat and helped the tanks and artillery.
Some of the engineers' acclaimed achievements during the war include constructing the Pentagon, which is the world's largest office building; the Alcan Highway to Alaska; and the Ledo and Burma Roads built through the mountains and jungles of Asia. They also supervised the Manhattan Project - the construction of the atomic bomb.