Corrected entry: You'd think Berger would clear up the mistaken identity mess during his journey to Vietnam or upon his arrival, and not just accept that he's been sent to fight a war he doesn't believe in under someone else's name. After all, there would be dozens of other soldiers who could verify that he is indeed not Claude Bukowski.
Corrected entry: Berger goes to Nam instead of Bukowski, having taken on his name and identity. His tombstone should say Claude Bukowski, not George Berger.
Correction: The real Claude could have cleared up the identity mix-up before the tombstone was engraved.
Correction: Berger probably did clear up the mistaken identity mess, his name is on the tombstone after all. But Berger was drafted too, in the opening scene in New York, Berger and the other guys are burning their draft cards. So Berger was supposed to be in the army and could not get out, just because of the identity misunderstanding.