Balls in the military is referring to the time 0000 or midnight.
Fred: Yo when do you have to wake up for work?
Dennis: I gotta get up at balls
Fred: Damn that sucks hopefully you dont have the balls to forever watch
Balls is a word to describe the male testicle, If you say balls it sounds really funny, but it's not funny.
Jake sat on his balls and screamed ow my balls.