Why does the author weave in reminders that a war is imminent?

Bradbury's story shows what happens to a society of people who no longer read and no longer learn. Also, Bradbury's story sends a warning to readers to be wary of government becoming too big and too controlling. War is mentioned with increasing frequency in the book which foreshadows its arrival near the end of the story. When war does finally arrive at the end of the book, it is quick and it is cataclysmic. It is also purifying. The war, which is over almost as quickly as it began, annihilates the city. Granger makes reference to the legend of the phoenix which burns itself up every so often and then rises anew from the ashes. He says that civilization can be like that. It can rise from the ashes of the old world and the new one can be better because people have learned from the mistakes of the past and maybe they won't make those mistakes again. The war in the story burns up the city, cleanses it, and allows for the possibility of a new and better society.