On this date in 1918, the American Army was in the second day of one of the last battles of The Great War, also known as The War to End All Wars, finally known as World War I.
History records the three-week battle as the Aisne-Marne Offensive, which proved to be the second costliest of the war for American soldiers. Almost 7,000 battle deaths occurred, more than twice as many as the third most costly, the Somme Offensive, and almost one-third as many as the most costly battle, the Meuse-Argonne Offensive.
Eight U.S. infantry divisions participated, including the 1st, 2nd, 3rd, 4th, 26th, 28th, 32nd, and 42nd, with elements of the 41st and 83rd Infantry Division supporting.   Some 250,000 Americans of the two million Doughboys serving overseas participated in this second largest battle of the war for U.S. troops.
The resulting casualties included 6,992 killed in action and 25,644 wounded. The German army was on the ropes, but still hanging on.
A previous German offensive in June, ordered by Gen. Erich Ludendorff, had made initial gains but then faltered.
Determined to gain ground before the American presence could be decisively felt, he ordered another offensive in the Marne salient. But, by this time German soldiers, long denied all but the barest necessities and facing ever failing morale from the home front, were lax in discipline and a warfighting spirit.
Ludendorff called this July offensive the Friedensturm, or Peace Offensive. That proved to be a mistake, for if not successful with such a grandiose title, the morale effect on German troops would be devastating, which proved to be the case.
It didn’t help the German situation that an influenza epidemic swept through the trenches, rendering already weak troops even weaker. Of course, the epidemic took a toll on Allied troops in the trenches also, but hit the German lines particularly hard.
Weak, and growing increasingly undisciplined, German troops began to desert and surrender to the enemy on the eve of each new offensive. That kept the prisoner of war compounds filled, which was quite all right with Allied leaders.
The French came up with a new tactic of forming a “sacrifice line,” whereby front-line troops were pulled back at night, leaving a small force to delay the expected German attack. When it came, the delaying force pulled back to a second “sacrifice line.”
After more wasted German artillery barrages against the second abandoned line, the delaying force pulled back again to a third line, which, unknown to the Germans, was the main line of resistance. The Germans chose not to waste artillery on the third line, and when the infantry attack was launched, it met stiff resistance rather than a sporadic delaying action.
This phase of the battle was over by noon of the first day. As the exhausted Germans paused to regroup, the Allies struck with an offensive of their own, which was the second phase of the battle.
Within a couple of days, the Germans were retreating all along the front. During the battle, some U.S. units had been attached to French units, an idea Gen. John Pershing, commander of the American Expeditionary Forces, adamantly opposed.
Jumping on U.S. success in this campaign, he lobbied hard with Field Marshal Foch for a separate American Army, operating under American officers. Following this battle, Foch granted Pershing’s request.
Another bit of history is that its fierce defense of the Marne River by the U.S. 3rd Infantry Division’s 38th Infantry Regiment gave it its nickname, “Rock of the Marne.”  The Great War was winding down.