Ghost Army, WWII's masters of illusion saved thousands

The Ghost Army was a secret US Army unit during World War 2 that used deception to save lives. Composed of artists and engineers, they created illusions with inflatable tanks, sound effects, and fake radio messages. Actors spread misinformation to mislead the enemy. Their efforts remained secret until 1996, when their contributions were finally recognized.

How did the Ghost Army create the illusion of a larger force?

When was the information about the Ghost Army declassified?