Battle of Saint-Mihiel, (12–16 September 1918), Allied victory and the first U.S.-led offensive in World War I. The Allied attack against the Saint-Mihiel salient provided the Americans with an opportunity to use their forces on the Western Front en masse. Although lacking some of the tactical skills of the French and British, the U.S. First Army carried the day through sheer determination and its multifaceted plan of attack. The battle was also noteworthy as the first major use in the war of the U.S. Army Air Service (precursor to the U.S. Air Force) led by William "Billy" Mitchell and the aggressive tank assaults by George Patton, who boldly led his charges from the front lines and not from the rear as many other officers did during the war.

Pershing, John J. John J. Pershing. Encyclopædia Britannica, Inc.

The American commander-in-chief in France, General John Pershing, had, in the main, fought off attempts to use his divisions piecemeal in support of French and British operations, preferring to hold them back to form a separate U.S. army. The attack on the Saint-Mihiel salient on 12 September gave him the opportunity to use the U.S. First Army in combat for the first time. The American part of the assault was to be conducted by two "super" corps, each with three divisions in attack and one in reserve. Two smaller French corps would provide support on the western part of the salient.

Erich Ludendorff, c. 1930. Archiv für Kunst und Geschichte, Berlin

General Erich von Ludendorff—now short of men and aware of the coming Allied offensive—had decided to withdraw from the salient to a shorter and more easily defended line to the rear. As the Germans were withdrawing, the Allies attacked. With much of their artillery not in place, the Germans were poorly prepared to maintain the front line, an advantage that the attacking Americans were quick to exploit. The relative ease of the initial American attack came as a surprise to Pershing, and he sent orders to his commanders to speed up their advance. By 13 September lead units of the U.S. First Army had met up with Allied troops advancing from the west. Three days later, the offensive was halted, with the salient in Allied hands. Pershing now dispatched his forces westward to take part in the forthcoming Meuse-Argonne offensive.

Losses: U.S., 7,000 casualties; German, at least 17,500, including 10,000 captured.