During Basic, sometimes you're so tired you can't even get up to piss. You're pushed beyond whatever limits you had set for yourself. You realize that your body can do things that you never imagined. But there are times when you don't think you can go on, and that's when your brother is there to lift you up and push you forward. He yells encouragement when the drill sergeant's yelling obscenities. You know that if you're ever caught by the enemy, your brothers will never stop looking for you. If you're hurt they'll help heal you. The Corps is a unit of many, not one, but dozens, thousands even, who have your back. You can smite one Marine, but a thousand will rose up to avenge him.