Well, if he doesn't, then why is he going back to the school and writing a confession? Aren't those indications of regret?
"I never killed anybody and I never developed an intense level of hatred for the enemy. Because my war ended before I ever put on a uniform; I was on active duty all my time at school; I killed my enemy there. Only Phineas never was afraid, only Phineas never hated anyone."
"All of them, all except for Phineas, constructed at infinite cost to themselves these Maginot Lines against this enemy they thought they saw across the frontier, this enemy who never attacked that way-if he ever attacked at all; if he was indeed the enemy."
Those would be very important quotes. I noticed they weren't in your essay. Another question, then: what do you think they mean? Do you think, for instance, that "the enemy" in the first quotation is the same as "my enemy"? Why does the author say that only Phineas was never afraid, only he never hated anyone, as if he were repeating the same point. Being afraid isn't the same as hating someone. Or is it?
And more questions: what is a Maginot Line? In what way did the various characters construct them? Why does the enemy never attack that way? (Hint: This last question is especially interesting, because in WWII the enemy did attack the Maginot Line. In fact, they attacked it at its strongest point using a cunning strategy involving gliders. In further fact, it was the success of the attack that allowed Germany to successfully conquer all of Europe so quickly. If the Line had held a bit longer, France and her Allies might have rallied). Why would it be in doubt if the enemy would attack at all?