"If I Die in a Combat Zone"

I thinks its odd that O'Brien is anti war in the beggining, yet he still decides to go to Vietnam anyways. Once he is there, of course he wants peace and the war to end, but it seems like he is kind of enjoying himself at the same time. It would be hard though if your whole town was cheering you on to go to war and you didn't really want to. I wonder why he did decide to go. Personally I would have done anything I could to not go and fight in a war that I didn't believe had a "good" cause.