of the dangers they face:

They were just kids; they just didn’t know. A nature hike, they thought, not even a war, so they went off into the shade of some giant trees-quadruple canopy, no sunlight at all-and they were giggling and calling each other yellow mother and playing a silly game they’d invented.

To some extent, Rat's innocence is a metaphor for the general lack of understanding of the Vietnam War among large sections of the American people. Rat and Curt are playing around because they don't really feel engaged with the conflict; this is someone else's war. Nevertheless, they're still deeply involved in this war whether they like it or not and soon Rat Kiley's innocence will be gone forever when Curt's blown to pieces after stepping on a landmine. One minute Rat and Curt are goofing off; the next minute one of them is dead.

Rat is completely changed by the experience. He was always an emotional character, but he was able to channel those emotions into telling stories. But in the aftermath of Curt's death he finds himself overwhelmed with emotions he simply can't handle. We see this when he writes a letter of condolence to Curt's sister. His mind subsequently begins to crack under the strain, and there is a tragic sense of inevitability about his eventual mental collapse. Rat shoots himself in the foot to try and get himself medically discharged. His sad decline is now complete. He has gone from being a take-charge kind of guy, always helping others, to a shell of his former self, desperate and hopeless.

Every character in Tim O'Brien's "The Things They Carried" changes as a result of war. The basic central theme of the story is precisely how men and women change after being touched by the unique and sad experiences that arise as a result of war.

Rat Kiley is perhaps the person who is most affected, although O'Brien is careful in not making one man's experiences seem of lesser or more importance than the others. All men are affected by war in one way or another.

However, what makes Rat's experience unique is that he is the life of the crowd. As a medic, he carries the cool things such as medicines, sweets, and even comic books. His humor tends to make things easier in a difficult situation. However, when Ted Lavender is shot, we begin to see the change in Rat in the way that he internalizes what is going on.

... right then Ted Lavender was shot in the head on his way back from peeing. He lay with his mouth open. The teeth were broken. There was a swollen black bruise under his left eye. The cheekbone was gone. Oh..[] Rat Kiley said, the guy's dead. The guy's dead, he kept saying, which seemed profound -the guy's dead. I mean really.

It is after the death of his friend Curt Lemon that Rat completely changes.He shoots a baby buffalo in the field, and even tries to shoot his own foot to get sent back home from the battlefield. Rat's is perhaps one of the saddest changes in the story because it shows how deeply war can break or make a man.