From Wikipedia:
The Ghost Army was a United States Army tactical deception unit during World War II officially known as the 23rd Headquarters Special Troops. The 1,100-man unit was given a unique mission: to deceive Hitler's forces and mislead them as to the size and location of Allied forces, while giving the actual units elsewhere time to maneuver. Activated on January 20, 1944, the Ghost Army arrived in Europe in May shortly before D-Day and returned to the US at the end of the war in July 1945. During their tenure, the Ghost Army carried out more than 20 deception campaigns, putting on a "traveling road show" using inflatable tanks, sound trucks, fake radio transmissions, scripts and pretense.
The logo was not used by the unit during WW2 but became associated with the unit after the war.
All joking and rivalry aside, we are one team, except during the Army/Navy game. Then you're on your own.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)