A U.S. Army field hospital in World War I. The Army Reserve's contribution to Army medicine in World War I was enormous. There were 9,223 Reserve medical officers by June 1917. A U.S. Army field hospital in World War I. The Army Reserve's contribution to Army medicine in World War I was enormous. There were 9,223 Reserve medical officers by June 1917. SHARE: Download: Full Size (0.11 MB) Tags: Photo Essays Credit: VIRIN: 168649-Q-EBY37-327.jpg Photo Gallery