Is the acronym for Commander Amphibious Task Force. This was the designation for the command group overseeing the Allied invasion of Normandy on D-Day, June 6, 1945
From the movie, "Saving Private Ryan": After landing on the beach at Normandy, Capt John Miller is sending status reports through his radioman. When the soldier is killed, Miller takes the radio and shouts "Cat F, Cat F," trying to contact the Task Force command. He notices that the radio is out of commission and throws it away.