Whenever most Americans hear about D-Day, they think about the June 6, 1944, massive Allied invasion of Normandy, France. Few ever think about an offensive, that could be described as America’s first D-Day invasion, that of an offensive launched on September 12, 1918 during World War I. Few may realize that the term D-Day was also used in World War II prior to the Normandy invasion as it was used in referring to earlier offenses in North Africa, Sicily, Italy and even in the Pacific in reference to fighting the Japanese.
Actually, D-Day is an abbreviation for Day-Day, referring to a specific date for an offensive when the date is to be kept secret or has yet to be determined. In the case of the Normandy invasion, it referred to a specific secret day but one that could have been varied pending weather conditions.
The first known US military use of the term D-Day actually refers to an order dating back to World War I which stated:
“In Field Order Number 9, First Army, American Expeditionary Forces, dated September 7, 1918: ‘The First Army will attack at H hour on D day with the object of forcing the evacuation of the St. Mihiel Salient.”
Saint-Mihiel is a town that lies about 140 miles due east of Paris, about 40-45 miles southwest of the Luxembourg border and only 20 miles south of Verdun, France. The city grew up around a Benedictine abbey that was built in 709 AD along the banks of the Meuse River.
Germany captured Saint-Mihiel in 1914 and had continued to occupy the city. It was strategically located south of Verdun, which Germany had their sights on. German forces quickly built a defensive V-shaped salient around Saint-Mihiel. American military leaders determined that they needed to liberate Saint-Mihiel in order to protect Verdun and to drive the Germans back to their own border, a mere 60 miles away. A number of railroad lines leading from Paris to the Western Front, went through or near Saint-Mihiel and it was vital that Allied forces free up those supply lines to help them defeat the Germans and drive them back over their border.
On this day, September 12, 1918, American forces numbering nearly 500,000, launched an all-out blitz attack on the 30-mile-wide German line at Saint-Mihiel, led by American General John Pershing. Actually, the Allied D-Day offensive on Saint-Mihiel involved the US First Army and one French Army Corps. One of Pershing’s junior officers was Colonel George Patton.
The Battle of Saint-Mihiel lasted from September 12 to September 16, 1918. The battle lines were strewn with trenches and other obstacles that made advancing on the enemy in those days, very dangerous. Five days of rain also hampered the troops as much of the battleground was muddy.
In addition to the massive artillery and tanks of the First Army, the Army Air Service also was involved in the D-Day offensive at Saint-Mihiel. They flew reconnaissance, did their best to destroy German observation balloons and they dropped bombs on the German lines.
After five days of some of the most intensive fighting of World War I, the American and French forces successfully drove out the German occupiers from Saint-Mihiel. Once the city and surrounding area was secured, Pershing took his forces and moved south the Argonne Forest where they joined efforts with British troops and proceeded to drive the German forces back into Germany and eventual defeat.
The Germans suffered 5,000 killed and wounded. The American forces suffered 7,000 killed or wounded and they captured more than 13,000 German prisoners and 466 pieces of artillery.
Sources for the above includes: America Fought Its First D-Day 96 Years Ago Today, And It Was A Huge Success; The St. Mihiel Offensive; Battle of Saint Mihiel, 12-13 September 1918; Saint-Mihiel Offensive; U.S. Launches Saint-Mihiel Offensive; The Air Battle of St. Mihiel; 12 September 1918: The St. Mihiel Offensive Opens; Saint-Mihiel