T he P arasites T hus B anished

Ender is promoted to command of his own army years earlier than usual, setting him up for resentment from his peers and pushing his abilities to the limit (intentionally). He is given command of the re-established Dragon Army, which had never won a third of its battles and was disbanded. Though dealing with fresh recruits, including the precocious Bean who is even smaller (and much smarter) than Ender himself was, Ender trains Dragon Army in unorthodox ways: he abolishes school-standard formations as they take a long time to learn and are highly inflexible, divides his army into five toons of eight instead of four of ten, and encourages each toon to act independently and take initiative during combat. Despite having only 3 weeks to train instead of the standard 3 months before their first battle, Dragon Army completely annihilates their first opponent with almost no casualties. After that, Dragon Army never loses a battle, despite engagements that are (deliberately) weighted against them.

After these three months spent in self-contemplation, Ender returns and is promoted to Command School, almost six years early, to learn to combat the Buggers in space instead of being restricted to the more abstract training games. He is taught by Mazer Rackham, the genius behind the previous human success against the buggers, and the first man to realize that the Formics are actually a hive mind (see group mind (science fiction)). There has been no way of communicating with the buggers, and they have shown no inclination to spare humanity their wrath; thus, plans for an invasion have been underway, and it is the command of this invasion that Ender is being trained for. Fortunately, he will be augmented by a cadre of his best friends (and the best commanders) from Battle School, including Alai, Petra, Dink, and Bean; Ender assigns them to individual flights or squadrons of ships while he remains in overall charge.

Once the team has meshed, the training begins, this time against Mazer Rackham. Ender and his ‘dream team’ begin to fight ever-more-challenging battles, in which his team must frequently fight with outmoded hardware, and the enemy frequently outnumbers them and quickly learns to adapt to Ender's tactics—even the ones that won yesterday's battle. Ender also begins to be plagued by mysterious nightmares which interrupt his sleep. Fatigued in mind and body, his team slowly succumbing to exhaustion, Ender begins to lose hope.

In Ender's final exam before graduating from Command School, he and his team find themselves in possession of a small fleet, approaching a planet that is literally swarming with Bugger ships, outnumbering his own force a thousand to one. Ender, by now, has had enough of being manipulated by the adults, and decides to flunk out of Command School—a true victory. He duplicates his final battle at Battle School and uses the Molecular Disruption Device to destroy the planet around which the Bugger fleet is orbiting (taking the surrounding fleet with it), demonstrating that he is far too ruthless to be trusted with command of an actual battle fleet.

However, when the simulation ends, Ender discovers that the ‘audience’ watching his ‘final exam’ is now in jubilation and delight. Rackham and Graff tell Ender that he has not been playing a game, and had never played against Rackham, but instead has been commanding real ships across interstellar distances; this task was made possible via the ansible, a form of instantaneous communication making use of Philotic Energy. This technology was discovered following the Second Bugger War, as the method of telepathic communication the Buggers used was reverse engineered. He has just commanded the fleet attacking the Buggers' home planet, and destroyed the entire race once and for all.