The role of a soldier
The protagonist quickly realizes that the role of a soldier is not to "do the right thing," but to execute the will of higher-ups who don't necessarily see the world the way he does. He sees there is an irony in his role, because his job is quite literally to betray himself. He does betray himself to execute orders, and several symbols in the text support that self-betrayal, like eating his dog, or lying to villagers with promises he never intends to keep.
The irony of heroism
When he comes back to America, he sees that he is regarded as a traitor of the common good of man, but ironically, he knows he is still a hero. His opinion of heroism has evolved to become something deeply ironic. Although he felt he was going to be a hero for going and doing something noble, he went and bore witness to unimaginable suffering, horror, and injustice, and he knows better than the public all the ways injustice shapes world politics. He is a hero for surviving that martyrdom.
His attachment betrayed
By looking to other people and objects for emotional comfort and support, it seems as if Wolff is punished by fate itself, because his attachments are constantly overturned by death. He attaches himself to the well-being of a dog, but then the locals sniff out that attachment and call it weakness, and before long, he is eating the dog. He attaches himself to a friend who dies, leaving him in even darker moods than before.
Maturity and innocence
Maturity means something unique to Wolff. When he sees Stu Hoffman trying to reunite to his father, he realizes that maturity is multifaceted. Although time has brought some maturity to his father, his constant exposure to near-death experience and mortal fear has given Stu a kind of maturity that can be likened to full-blown PTSD. If someone asked Stu, "What does maturity mean for you?" he might say, "We're all going to die." That is radically different than what his community means by the word.
Honor and warfare
There is an irony in warfare about honor, because on one hand, honor seems to imply fighting for the right cause, but in the experience of the soldiers, that isn't what it actually feels like to fight in war. There are people trying to kill them, and their job is to overcome their fear and weakness to execute the threats and survive. Their honor is their willingness to do violence to save their own lives, which seems antithetical to what the word seems to connote. Their view of honor is closer to Greek or Hindu honor, because it has to do with decisive action and the acceptance of one's responsibility in one's own survival.
