Just after the United States declared war in April 1917, Columbia medical personnel, in collaboration with Presbyterian Hospital, established the first American base hospital in the Bronx. Known as the United States War Hospital No. 1, it trained Columbia doctors and nurses for deployment to France. Some of these helped to establish Base Hospital No. 2 in Étretat, France. Others joined mobile medical units, specially equipped convoys of automobiles, to bring medical care close to the front lines, reducing the time that elapsed before wounded soldiers were treated and thereby saving lives.