Untested U.S. squadrons were initially sent to a fairly inactive sector of the Front north of Toul to acquire combat experience at a minimum risk. On April 8, 1918, the 1st Aero Squadron was assigned to an aerodrome at Ourches, and the next day the 94th Aero Squadron was assigned to an aerodrome at Toul. The 94th was soon joined by the 27th, 95th and 147th Aero Squadrons to form the 1st Pursuit Group, while the 1st Aero Squadron was joined by the 12th and 88th to form the 1st Corps Observation Group. Early in July when a German build-up was noted in the area of Chateau-Thierry, all seven units were moved westward to reinforce the French on the Marne River. Aerial combat for the seven U.S. squadrons over the Marne was much more intense than it had been at Toul. Often outnumbered four to one, they were pitted against some of Germany's most experienced units, including the famous von Richthofen squadron with Germany's latest pursuit, the Fokker D. VII. Despite heavy losses, U.S. units went out daily to assist French and British and by mid-August the German threat had been thwarted. The U.S. squadrons then moved to the St. Mihiel sector to prepare for the first large-scale American offensive. http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=689
