On August 30, 1918, in Belfort, France, a small town near the German border, Colonel Arthur L. Conger of the American Expeditionary Force (AEF) plants a copy of a false operational order for an impending Allied attack in a wastebasket; as intended, it is later found and removed by a German agent.
The Belfort Ruse, as the trick was dubbed, was the result of a suggestion by the French commander in chief, Philippe Petain, who was alarmed by the lack of security surrounding the upcoming Allied offensive near St. Mihiel, France. Planned for September 9, 1918, it was to be the first significant operation of the war under United States command; French troops were set to take part as well. The German-held salient near St. Mihiel, south of Verdun, had long plagued the Allies in France; it blocked the transport of troops and supplies on the railway line between Paris and Nancy, while posing a danger to any French offensive operation in the Meuse-Argonne region immediately to the west of the salient and providing the Germans with a forward defensive base that protected their all-important stores of coal and iron. The French had failed repeatedly to capture the salient; now it was time for another attempt.
After learning that the plans for the offensive were being talked about in Paris, Petain wrote a personal missive to the American commander in chief, General John J. Pershing, suggesting a ploy to misdirect the Germans as to the details of the upcoming attack. Pershing agreed, and with French assistance the Americans planted the false order in a Belfort hotel, presumably one where the French knew a German agent was on the staff.
The Belfort Ruse was designed to trick the German High Command into believing that the thrust of the Allied offensive, which would begin less than two weeks later, on September 12, in the St. Mihiel salient, would instead be launched near Belfort toward the German town of Mulhausen (Mulhouse), just across the border. The extent to which the ruse proved successful is debatable; some German divisions were indeed diverted to the Belfort region, but these troops did not come from St. Mihiel. The German command, aware of the impending attack on the salient, apparently made the decision not to hold it, and to withdraw from the area. This withdrawal was still in progress when the U.S. attacked on September 12, and by September 16 the AEF controlled the area.