While riding inside the flying carriage, Matthew and Leah narrated everything that they had experienced during the war. The swarm of ants that covered both the land and the sky, and the sacrifices that were made to prevent the fort from being overrun by the invaders.
William listened with a serious expression to his Big Brother's and Big Sister's tales because he had no idea how the war between the Hellan Kingdom and the Two Dynasty transpired. Issei, David, and Lily didn't tell him anything about the war and prevented him from making contact with Ian, who was constantly nursing his Spiritual World.
He understood that the Gods didn't want him to worry, so that he could train in peace. Now that his training was over, he wanted to know everything, so that he could formulate his next course of action.