Explain the significance in the shifting of Finny's attitude about the war.

During the summer session, Finny and Gene enjoy their carefree lives at Devon as innocent, adolescent boys. As World War II begins, Gene recalls Finny saying that he does not believe the Allies bombed Central Europe. Gene explains Finny's reasoning by saying,

Bombs in Central Europe were completely unreal to us here, not because we couldn’t imagine it—a thousand newspaper photographs and newsreels had given us a pretty accurate idea of such a sight—but because our place here was too fair for us to accept something like that. We spent that summer in complete selfishness, I’m happy to say (Knowles 12).

Later on, Gene becomes envious of Finny and misinterprets their friendship. Gene then shakes the branch of a tree, making Finny fall and break his leg. After Finny breaks his leg, he can no longer participate in the activities preparing the students for enlisting in the military, and he feels left out. Finny refuses to believe that World War II is happening and tells Gene that the entire war is a conspiracy created by old men.
Toward the end of the story, Finny ends up reinjuring his leg when he attempts to escape from the mock trial held by the boys, where he realizes that Gene purposely made him fall. In chapter 12, Gene visits Finny in the infirmary, and Finny finally acknowledges that there is a war. Finny tells Gene that he has been desperately trying to enlist in any branch of the military. Finny says,

I’ll hate it everywhere if I’m not in this war! Why do you think I kept saying there wasn’t any war all winter? I was going to keep on saying it until two seconds after I got a letter from Ottawa or Chungking or some place saying, "Yes, you can enlist with us" (Knowles 103).

Gene responds by telling Finny that he would be a terrible soldier because he would make friends with the enemy and end up playing cards with them in the middle of a battle.
The shifting of Finny's perception regarding the war illustrates his diminishing innocence. In the summer session, Finny doubts that there is war simply because he is naive and preoccupied with the tranquil setting of Devon in the summer. After Finny breaks his leg, he refuses to acknowledge the war in an attempt to protect his emotions. Finny finally accepts that there is a war and that he will not be able to participate because of his serious injury. The fact that Finny finally acknowledges that there is a war reveals his loss of innocence and emphasizes his emotional pain.