Mazer Rackham

Basically the two fight. After making this request, the next day there is an old man sitting cross-legged on his floor. Ender waits for him to speak, but he does not speak even when addressed. His door is locked, so he does his morning exercises. One time the man grabs him but then retreats, so Ender ignores him. When Ender's guard is down, the old man grabs him violently and tells him that he should never turn his back on the enemy. This man will be his teacher and his enemy, because "there is no teacher but the enemy." As the man lets him go, Ender kicks him, and they fight. They hurt each other, and when Ender finally asks the old man his name, his new teacher says: "Mazer Rackham."