The bad guy?

So far I've gotten to page 100 of the novel and I haven't been able to clearly identify the antagonist of the story. Some would be quick to point out at that the antagonist of the story would be the country of Vietnam itself. However, I do not find this to be true. While Vietnam and its army were what the American soldiers were fighting and the place itself is what caused the misery and death of several, I find the position of the antogonist to lie in another. I think that its the men themselves. Some of the men drive themselves crazy even when there is no danger in what they think is dangerous. For example, in the chapter "Enemies", the man who beats the other soldier's nose in starts to get paraniod about the guy when he comes back thinking that he is going to want revenge. His imagination and mind is what starts to drive him crazy until he finally breaks. At the end of the chapter, we find out that the other guy did not want to seek revenge in the first place. So one of the main things that the soldiers had to worry about was simply themselves.