Attached is a thumbnail history of the United States Army Ambulance Service, which first arrived in June of 1917.
"All through the hard French fighting of 1917 the 6,000 American ambulance drivers kept steadily at work in every sector of the French front. It was not until March, 1918, that the first sections of the service found themselves helping in battles with the fighting regiments of their own Army."
Many of the volunteers were college men, such as the poet E.E. Cummings, who wrote an account of his days as an ambulance driver during the war.