Finny decides spontaneously to start the games by burning a copy of Homer's "Iliad" which shows his care free attitude toward the war efforts, which parallels Achilles disinterest in fighting the battle with the Trojans. As Achilles had a weakness, Finny's Achilles heel is his innocent perspective which leads him to always trust his friend which leads to his crippling fall. Irony is a literary technique of indicating, through character or plot, an attitude opposite that which is actually stated.
It is, therefore , ironic that the Iliad which is a epic story of a hero, is sacrificed in the fire of Finny's games which parallels the fire of Gene's inner emptiness which will burn up Finny's life.
Upon arrival of the telegram from Leper, the game and a spontaneous huge snowball fight is at its high point and the bedlam of the boys is brought to a screeching halt. The privileged and innocent life of the boys is being ended by the war. So, as the winter carnival is halted by the Lepers' letter, so is the enthusiasm and free spiritedness of the boys is ending without their having much of a say about it.