Pretty near exact. The catch is pointed out by Doc to Yossarian, a precis being: No madman can serve in the armed forces, so to get out of the forces Yossarian wants to pretend to be mad. The problem is that under regulations the mad person must ask to leave. But by army definition anyone who is sane wants to leave, so anyone asking to leave must be sane, wether they are mad or not. The net result is that madness is no way out. The only way to escape is to paddle a liferaft to Sweden.