Yossarian, a bombardier during World War II, whose frantic obsession every time he goes up on a mission is "to come down alive." The real enemy for Yossarian and his rag-tag bunch of friends is the bureaucracy of the military, inverting logic at every turn. The pinnacle of this is Catch-22, a military by-law which states that if you fly your missions, you're crazy, and don't have to fly them; all you have to do is ask. But if you ask not to, then you're sane, and so you have to fly them.