After a month of preparations, on September 12 the American 1st Army, along with four French divisions, attacked the German salient at St. Mihiel, where more than sixty-thousand soldiers were dug in. It was the Americans’ debut as an independent battle force. The French town had been held by the Germans for four years, and, wrote John J. Pershing, commanding general, “The salient was practically a great field fortress. It had, however, the characteristic weakness of all salients in that it could be attacked from both flanks in converging operations.”

A fearsome four-hour barrage preceded the American advance that morning. The first attack on the salient, from the south across the Moselle Valley, began in drizzle at about 5:00 A.M. and was followed by an Allied bombardment of the western side three hours later. “There was a chill breeze blowing,” Pershing later recalled, “and its direction was such that no sound of firing could be heard from the artillery in our immediate front. … The sky over the battlefield, both before and after dawn, aflame with exploding shells, star signals, burning supply dumps and villages, presented a scene at once picturesque and terrible.” After seventeen months of training, the general observed with tempered pride, American soldiers were fighting and dying under their own flag.

The 1st Army made such quick work of the German barbed-wire barricades that day—using cutters, axes, bangalore torpedoes, and bridging across fences with chicken wire—that the French general Henri Pétain later sent a group of his officers to visit the site to learn their techniques. The Americans had advanced five miles into the south side of the salient by midnight of the twelfth, completing almost two days of the plan in one long day’s effort. Pershing’s line was in place by the next day, when his southern 1st Division and western 26th joined at Vigneulles-lès-Hattonchâtel, trapping the Germans. By September 16 the salient was pinched off, nearly sixteen thousand German soldiers had been taken prisoner, and the long-captive town of St.-Mihiel was freed, although a good deal of it had been destroyed in the barrage. The Americans suffered seven thousand casualties in the operation.