"Engineers at War" describes the role of military engineers, especially the U.S. Army Corps of Engineers, in the Vietnam War. It is a story of the engineers' battle against an elusive and determined enemy in one of the harshest underdeveloped regions of the world. Despite these challenges, engineer soldiers successfully carried out their combat and construction missions. The building effort in South Vietnam allowed the United States to deploy and operate a modern 500,000-man force in a far-off region. Although the engineers faced huge construction tasks, they were always ready to support the combat troops. They built ports and depots, carved airfields and airstrips out of jungle and mountain plateaus, repaired roads and bridges, and constructed bases. Because of these efforts, ground combat troops with their supporting engineers were able to fight the enemy from well-established bases. Although most of the construction was temporary, more durable facilities, such as airfields, port and depot complexes, headquarters buildings, communications facilities, and an improved highway system, were intended to serve as economic assets for South Vietnam. This volume covers how the engineers grew from a few advisory detachments to a force of more than 10 percent of the Army troops serving in South Vietnam. The 35th Engineer Group began arriving in large numbers in June 1965 to begin transforming Cam Ranh Bay into a major port, airfield, and depot complex. Within a few years, the Army engineers had expanded to a command, two brigades, six groups, twenty-eight construction and combat battalions, and many smaller units.