A troop sleeper was a railroad passenger car which had been constructed to serve as something of a mobile barracks (essentially, a sleeping car) for transporting troops over distances sufficient to require overnight accommodations. This method allowed part of the trip to be made overnight, reducing the amount of transit time required and increasing travel efficiency. Between December 1941 and June 1945 U.S. railroad carried almost 44 million armed services personnel. As there were not enough cars and coaches available to meet the massive need for troop transit created by World War II, in late 1943 the U.S. Office of Defense Transportation contracted with the Pullman Company to build 2,400 troop sleepers.