Most Americans associate the term D-Day with June 6, 1944, when a massive Allied force sailed across the English Channel to storm the beaches of Normandy, France, with the support of paratroopers dropped behind enemy lines. That date was a major turning point of World War II, opening a new western front against the Germans that led to the liberation of France.But June 1944 was not the only time the term 'D-Day' had been used to specify the day of a major attack. D-Day also signified the opening day of every amphibious assault of World War II, including earlier battles in North Africa, Sicily, Italy, and against the Japanese in the Pacific.
In fact, the earliest known use of the term dates back to World War One. The U.S. Army Center of Military History identifies this distinct origin: "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.'"
The term "D-Day" is short for Day-Day, designating the day when an operation is to begin in cases where that date hasn't yet been determined or is kept secret, according to the Center of Military History.
Following the September 7 order, the first D-Day took place September 12, 1918, when more than half a million American troops attacked a 30-mile-wide German position that jutted 15 miles into Allied lines, known as the St. Mihiel salient. Known today as the Battle of St. Mihiel, it was the first independent American offensive of the war and the single largest American military undertaking up to that point.
The Americans led the St. Mihiel offensive under the newly organized First Army, consisting of 550,000 American and 110,000 French troops. The operation relied on 3,010 artillery guns, none of which were U.S.-made. All of the 267 light tanks used in the offensive were French-manufactured, though more than half were manned by U.S. troops. The British promised to furnish the Americans with heavy tanks to crush the enemy's barbed wire defenses but in the last moment notified the Americans that the tanks couldn't be provided.
"The salient was practically a great field fortress," wrote the commander of the American army in France, General John Pershing. "It had, however, the characteristic weakness of all salients in that it could be attacked from both flanks in converging operations. Out heaviest blow was to be from the south where there were no great natural features to overcome, while the secondary attack was to come from the west and join the main drive in the heart of the salient."
The map below shows the plan of attack. The American IV and I Corps attacked from the south in conjunction with the American V Corps from the west in order to close the salient in a pincer movement at the town of Vigneulles, while French troops attacked the tip of the salient.
High casualties were expected, as U.S. Colonel George Marshall, one of the planners of the St. Mihiel Offensive, wrote in his account of the battle:
About fifty thousand (50,000) casualties was the percentage normally to be expected and hospitalization was prepared accordingly. Nevertheless, if we suffered that many casualties during the brief period involved, the American people, not accustomed, as were our Allies, to such huge payments in human life, would have seized upon the criticism of any Allied official as a basis for condemning our own Commander in Chief.
Marshall suggested to General Pershing that they precede their attack with an 18-hour artillery bombardment, aimed at the Germans' barbed wire defenses. Although long bombardments sometimes lasting days were the norm in World War One, Pershing decided to limit the bombardment in this instance to just four hours, in order to retain the element of surprise. The attack began at 5 a.m. on the morning of September 12.
Their French allies considered the enemy's barbed wire defenses impassable until engineers, artillery, and tanks could remove them, but impatient American troops simply walked over the barbed wire. 800 astonished French officers visited the American positions two days after the battle to see for themselves how they got through the obstacles. "A French officer in this party told me afterwards that the evidence on the ground convinced him that our infantry had walked over the wire, but he thought perhaps they were assisted in this remarkable performance by the size of their feet," Marshall recounted.By the evening of September 12, most American troops attacking the salient's southern boundary were a day ahead of their scheduled objective. "The German resistance on this part of the front was disorganized by the rapidity of our advance and was soon overcome," Pershing wrote.
Initially, the American troops attacking from the west and French troops assaulting the salient's tip made smaller advances due to tougher resistance. But by the afternoon of September 12, the Americans were encouraged by the news that German troops were retreating from the salient, burning French villages in their wake.
By 6 a.m. on September 13, the Americans had entered Vigneulles from both the southern and western directions. "The salient was closed and our troops were masters of the field," Pershing declared in his account of that moment.Later that day, the troops reached their final objective of the offensive, completely erasing the bulge of German-held territory that had persisted for four years. Several German counterattacks were repulsed on the 13th, while in other areas the Germans continued a disorderly retreat. The Americans mounted local operations through September 16 to secure their grip on the newly conquered territory.The successful offensive resulted in 7,000 casualties on the Allied side, far below the expected number of 50,000. The Americans captured 16,000 prisoners and 450 enemy guns.
"On my visit to several corps and division headquarters the following day, I found all jubilant over the victory and overflowing with incidents of the fighting, reciting many feats of heroism among the troops," Pershing wrote. "In one or two cases, the keen rivalry between the adjoining divisions had resulted in friendly controversies between them as to which should have the credit for the capture of certain localities."
The American public was exposed to the term "D-Day" by at least 1919, when it appeared in an article published in Collier's Weekly by Colonel Frederick Palmer, titled America's Greatest Battle. "We had thirteen days from Saint-Mihiel 'D' day (the day of attack) to the Argonne 'D' day, in which to move all of our troops and all they required, to bring up our heavy artillery, prepare our dumps of ammunition, to assemble our trains, and school our ground divisions to the work," Palmer wrote in that article, also referring to the September 27 Battle of Argonne that immediately followed the Battle of St. Mihiel.
"The St. MIHIEL Salient, that needle point on the Western Front for four long years, had been nipped off," wrote American Captain Barnwell Rhett Legge in a 1919 account. "The First Army, but recently come into being, gave to the world tangible evidence of America's power."
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