What does the patch A in a circle symbolize in World War 2?

3rd Army - commanded by Gen George Patton.

Patch is a BLUE circle with a RED border and a WHITE "A". 6th Army was a GREEN circle with a WHITE 6-pointed Star with RED Trim and a RED "A" in the center of the star. The A is very prominant. Anti-Aircraft Command was a WHITE circle with BLUE trim and two(2) RED "A" in the center. Allied Forces HQ was a circle with "AF" in the center.