General Pershing places the four combat ready US Divisions in France under French command.

You will constantly hear, and now without good reason, that General John Pershing was very reluctant to place US troops under European Command.  Indeed, he was reluctant to do so.

Indeed, Pershing basically disagreed with European strategy in general and wasn't at all impressed by the argument that French and British forces were trained and combat experienced.  He felt that their experience was one of failure.  He didn't agree with concepts of trench warfare.  He was a cavalryman and like the later cavalry generals of World War Two, such as Patton, an understudy of his, he totally disagreed with concepts of static warfare.

Pershing hoped to deploy large, square, American divisions backed by cavalry regiments in mobile warfare and was largely prepared to ignore Allied pleas to commit U.S. troops to European command. But he was also savvy to the battlefield situation. The U.S. had been rotating men from the four divisions then in France to the front to get them exposed to combat.  On this day he committed the four U.S. divisions to French command, in light of the massive German spring offensive.  As the offensive was primarily directed at the British at this point, the French would not immediately call upon them.