In 1944, specially trained army combat engineers were assigned to blow up underwater obstacles and clear defended ports during the invasion of Normandy. During World War II, the Army Corps of Engineers in the European Theater of Operations was responsible for building numerous bridges, including the first and longest floating tactical bridge across the Rhine at Remagen, and building or maintaining roads vital to the Allied advance across Europe into the heart of Germany. In the Pacific theater, the "Pioneer troops" were formed, a hand-selected unit of volunteer Army combat engineers trained in jungle warfare, knife fighting, and unarmed jujitsu (hand-to-hand combat) techniques. Working in camouflage, the Pioneers cleared jungle, prepared routes of advance and established bridgeheads for the infantry, as well as demolishing enemy installations.