How did Peter win

They hear the rich sound of a horn, and look back to see the wolf that was sent by the Witch. It is threatening to kill Susan, who has climbed a tree before alerting them with the horn she received from Father Christmas. Peter, though not feeling particularly brave, recognizes that his feelings make no difference, and that he must save his sister. He attacks the wolf and sinks his sword into its heart, killing it. Aslan sees a second wolf, but this one is running away. He sends the centaurs and the eagles gathered on the hilltop to follow it, in order to find the Witch and to rescue Edmund.