It all began on November 2, 1917, at 3:00 a.m. after a forty-five minute artillery barrage: 240 highly experienced German soldiers (at least two of them were wearing American uniforms) descended upon the American trench and began making quick work out of those within:
"The Germans retired after a period of probably fifteen minutes carrying all their dead and wounded, and eleven of our men as prisoners... They cleaned the trench of every piece of our equipment they could lay their hands on, and left none of theirs behind as evidence of the unit to which they belonged."
"Nine days later, utterly fatigued, grimy, unshaven and covered with mud, we were relieved by the French who once more took their places in the 'quiet sector'"
The U.S. would not make their first trench raid until March, 1918.
Some decades later it was discovered that a full sixty percent of the invalided Doughboys were mentally deficient, and the Army was unable to screen them out - you can read about that here