I agree with Jessica. I think that O'Brien uses repetition in this
chapter because this is a major event in his life. The shock of having
taken a life shocked him significantly. But what I think shocked him
the most was how automatic his reaction of throwing the grenade was
when he saw the man walking on the trail. "His jaw was in his throat,
his upper lip and teeth were gone, his one eye was shut, his other eye
was a star-shaped hole, his eyebrows were thin and arched like a
woman's, his nose was undamaged, there was a slight tear at the lobe
of one ear," (118). O'Brien relives these details over and over again
because he did not know he was capable of such a violent act. He
suspected he would have reacted differently, and by not even thinking
twice about throwing the grenade, he traumatizes himself. But I don't
think he repeats himself to help himself forget. It represents the
repetition of those memories that he relives. I think his hopes are to
demonstrate to the reader that the memory of his actions will never
leave him. He will never forget because he is still unable to believe
how easily he threw the grenade that killed the man walking on the
trail.