Admiral McKenzie was in charge of the Navy, and he was visiting his colleague General Marshall, who was in charge of the Army.  McKenzie arrives at the military camp and is greeted by Marshall.  They both walk around the place, and McKenzie asks: "So how are your men?"

"Very well trained."

"I hope so.  You see, my men over at the Navy are so well trained, you could see they're the bravest men all over the country."

"Well, my men are very brave, too."

"I'd like to see that."

So Marshall calls private Cooper and says: "Private Cooper!  I want you to stop that tank coming here with your body!"

"Are you crazy?  It'd kill me, you idiot!  I'm out of here!"

As private Cooper ran away, Marshall turned to a bewildered McKenzie and said, "You see?  You have to be pretty brave to talk like that to a general."