The Battle of Saint-Mihiel was a World War I battle fought between September 12 - 15, 1918, involving the American Expeditionary Force and 48,000 French troops under the command of U.S. general John J. Pershing against German positions. The United States Army Air Service (which later became the United States Air Force) played a significant role in this action.
The attack at the St. Mihiel salient was part of a plan by Pershing in which he hoped that the U.S. would break through the German lines and capture the fortified city of Metz. It was one of the first US solo offensives in World War I and the attack caught the Germans in the process of retreating. Hence their artillery was out of place and the Americans were more successful than they otherwise would have been. It was a strong blow by the U.S. and increased their stature in the eyes of the French and British forces. However, this battle again illustrated the critical role of artillery during World War I and the difficulty of supplying the massive World War I armies while they were on the move. The U.S. attack faltered after outdistancing their artillery and food supplies as muddy roads made support difficult. The attack on Metz was not realized as the Germans refortified their positions and the Americans turned their efforts to the Meuse-Argonne offensive.
General John Pershing thought that a successful Allied attack in the region of St. Mihiel, Metz, and Verdun would have a significant effect on the German army. General Pershing was also aware that the area's terrain setting dictated that the "clearing" of the rail and road communications into Verdun, and therefore the loss of the German railroad center at Metz would be devastating to the Germans should the Americans capture it. After these goals were accomplished, the Americans could launch offensives into Germany.
Prior to the American operation, the Germans installed many in-depth series of trenches, wire obstacles, and machine-gun nests. The battlefields' terrain included the nearby premises of three villages: Vigneulles, Thiaucourt, and Hannonville-sous-les-Cotes. Their capture would accelerate the envelopment of the German divisions near St. Mihiel. The American forces planned to breach the trenches and then advance along the enemy's logistical road network.
The Germans knew many details about the Allied offensive campaign coming against them. One Swiss newspaper had published the date, time, and duration of the preparatory barrage. However, the German army stationed in the area of St. Mihiel lacked sufficient manpower, firepower, and effective leadership to launch a counter-attack of its own against the Allies. Thus, the Germans decided to pull out of the St. Mihiel salient and consolidate their forces near the Hindenburg Line. The Allied forces discovered the information on a written order to the German Group Armies von Gallwitz.
Although the AEF was new to the French theater of war, they trained hard for several months in preparation of fighting against the German armies. Also, the British use of armor at the Battle of Cambrai impressed General Pershing so much that he ordered the creation of a tank force to support the AEF's infantry. As a result, by September 1918, Colonel George S. Patton Jr. had finished training three tank brigades at Langres, France for an upcoming offensive at the St. Mihiel salient.
Another reason for the American success was the audacity of the small unit commanders on the battlefield. Unlike the World War One officers that commanded their soldiers from the rear, Colonel Patton and his subordinates would lead their men from the front lines. They believed that a commander's personal control of the situation would help ease the chaos of the battlefield.