Ender's Game
Orson Scott Card
 This story begins as Ender is made the commander of Dragon Army at Battle School, an institution designed to make young children into military commanders to fight in the next interstellar war against an unspecified enemy. Armies are groups of students that fight mock battles in the Battle Room, a null gravity environment, and are subdivided into squads known as "toons". Due to Ender's genius in leadership, Dragon Army goes on to dominate the competition, despite the teachers' attempts to put obstacles in their way. After his nineteenth consecutive victory, Ender is told that his Army is being broken up and his toon leaders promoted to be commanders in their turn, while he is being transferred to Command School for the next stage of his education. Here, a veteran named Mazer Rackham tutors him in the use of a space battle simulator. Eventually, many of his former toon leaders are brought along to serve under him once more. Once they are familiar with the simulator, they begin to fight a series of what Mazer tells them are mock battles against a computer-controlled enemy. Ender's team wins again and again, finally destroying a planet that the enemy fleet seems to be protecting. Once the battle is over, Mazer tells an exhausted Ender that all of the battles were in fact real, the children's commands having been relayed to the actual fleet, and that he just destroyed the enemy's home world and ended the war.