18 JUL--This Day in US Military History

1918 – Various French British and US forces launch a counterattack against the German forces in the salient they hold between Soissons and Reims in Champagne.

The fighting becomes known as the Second Battle of the Marne. The attack is led by three French armies, the Tenth under General Charles Mangin, the Sixth under General Jean Degoutte, and General Henri Berthelot’s Fifth. Support is offered by the French Ninth Army under General M.A.H. de Mitry.
The main attack involves the French Tenth Army and its spearheaded by the US 1st and 2nd Divisions, which take 8,000 prisoners and 145 artillery pieces for the loss of 5,000 casualties.
Elsewhere, General Hunter Liggett’s US I Corps fights alongside the French Sixth Army, which advances into the salient from the west along the Ourcq River. Three further US divisions for General Bullard’s III Corps are attached to the French Ninth Army which is driving into the salient from the south close to Chateau-Thierry.
The German defenders begin to collapse under these converging attacks and Ludendorff has to contemplate an urgent withdrawal.

https://thisdayinusmilhist.wordpress.com/2005/07/18/july-18/