The Ghost Army was an Allied Army tactical deception unit during World War II officially known as the 23rd Headquarters Special Troops (Operation Quicksilver). The 1,100-man unit was given a unique mission within the Allied Army: to impersonate other Allied Army units to deceive the enemy. From a few weeks after D-Day, when they landed in France, until the end of the war, they put on a "traveling road show" utilizing inflatable tanks, sound trucks, fake radio transmissions, scripts and pretence. They staged more than 20 battlefield deceptions, often operating very close to the front lines. Their story was kept secret for more than 40 years after the war, and elements of it remain classified. The unit was the subject of a PBS documentary The Ghost Army in 2013.
Inspiration for the unit came from the British units who had honed the deception technique for the battle of El Alamein in late 1942, as Operation Bertram. The unit had its beginnings at Camp Forrest, Tennessee, and was fully formed at Pine Camp, NY (now Fort Drum), before sailing for the United Kingdom in early May 1944. In Britain they were based near Stratford upon Avon, and troops participated in Operation Fortitude, the British-designed and led D-Day deception of a landing force designated for the Pas-de-Calais.
Some troops went to Normandy two weeks after D-Day, where they simulated a fake Mulberry harbour at night with lights which attempted to draw German artillery from the real ones. After which the entire Unit assisted in tying up the German defenders of Brest by simulating a larger force than was actually encircling them.