The final chapter, of the things they carried"the lives of the dead", doesn't seem to be about vietnam, but yet at the same time, seems to encompass one of the messages of the entire novel. what is that message, and how did linda's death influence tim's o'brien's war experience and his ability to write this novel?

One of the messages of the entire novel is the close interrelation amid life and death.

Linda's death influenced O'Brien's war experience in a way that the reason why he writes the novel is really to make sense of his own life and particularly how his life is related to other people's death.

O'Brien uses Linda's death to convey and illustrate his loss of innocence, due there's love and joviality involved in between both of them; thus when Linda dies, O'Brien's innocence also dies by default.