The military engineers who supported the U.S. Army in Vietnam wrote a proud record of achievement that spanned nearly two decades of war. Starting with a handful of advisers in the mid-1950s, Army engineers landed in force with U.S. ground units in 1965 and before long numbered more than 10 percent of the U.S. Army troops committed to the fight. Working in one of the world's harshest undeveloped regions, and under constant threat from an elusive and determined foe, the engineers met every test that came their way. They built ports and depots for a supply line that reached halfway around the globe, carved airfields and airstrips out of jungle and mountain plateaus, repaired roads and bridges to clear the advance for the combat infantryman, and constructed bases for an army whose communications grew in complexity with each passing year. They were often found in the thick of the fighting and fought as infantrymen as part of a long tradition of fighting while building. When the U.S. involvement in the Vietnam War began to wind down, the engineers were given another demanding mission, imparting to the South Vietnamese Army their specialized skills in construction and management. They left in place a robust infrastructure to support the South Vietnamese as they vainly struggled for survival against the armored spearheads of the North Vietnamese Army.Engineers at War is the eleventh volume published in the United States Army in Vietnam official series. Like its companion volumes, it forcibly reminds us that the American soldier in Vietnam was courageous, infinitely adaptable, and tireless in pursuit of the mission. For the engineers, that mission and their comrades sustained them, in the best engineer tradition, even as the political and popular will to sustain the fight diminished. Their story and dedication should inspire all soldiers as they face a future of sustained operations around the world.