Insignia for the 23rd Headquarters Special Troops
Imagine you are a German scout in the Rhine River Valley during waning days of World War II. Your mission is to gather reconnaissance on an Allied unit near your unit. As you sneak up on the camp you see a massive convoy of trucks and tanks in the distance. You briefly question why the large convoy is so poorly camouflaged, but more importantly you realize your unit is in serious trouble, as they have no idea how much fire power the Allies have in the region. You hurry back to your unit to tell them you need to retreat in the face of such power.
Sadly you were duped. It turns out there were not nearly as many tanks as you originally thought, at least not as many tanks made of metal. A couple weeks after D-Day the Allies started deploying the "Ghost Army," a division made up entirely of actors and inflatable tanks. The whole purpose of the unit was to cause confusion in the German ranks. The secret of the American inflatable tanks was kept in the dark until the program's declassification in 1996.