After coming home from school after beating up the bully named Stilson, a man named Colonel Graff comes to ask Ender to join at Battle School to become a soldier to fight off the threat of the Buggers.
Ender says yes to Colonel Graff and he and some other kids travel to battle School. Meanwhile on the ship Ender gets into a fight and he breaks another kid's arm.
After training at the school and surpassing everyone in his class, he is moved to the Salamander army but the leader, Bonso, doesn't let him participate in any of the battles.
After being transferred between multiple armies, Ender finally gets to lead his own army named the Dragon army. In the past the Dragon army has never won one third of their games but with Ender they have won every one of them. But Ender has lost some friends in the process.
Finally, Ender gets transferred to Command School on Eros, because he is the best in the school and they need commanders for their army.
Ender trains with Mazer Rackham, a famous war general from the First and Second Bugger invasions.