What is Finny's theory about the war, and how does his injury influence his attitude toward the war in A Separate Peace?

After his injury, the once "gung-ho-for-the-war" Finny tells Gene and Brinker that the war is simply a ploy designed by fat old men to do away with their competition (young men) by sending them into combat. He even asks Gene,

" 'Have you swallowed all that war stuff?' " (114).

When Finny first verbalizes his theory, Gene does not understand why Finny would have so drastically changed his attitude toward the war.  However, after Finny is injured yet again, Gene discovers that Finny's disillusionment from the war stems from Finny's not being able to participate in the war effort.  He had been writing military leaders from all around the world to see if anyone would accept him.