In Orson Scott Card's science fiction novel, young teens are trained in combat simulations. One, Ender Wiggin, proves to be a natural tactician and leader, so his training is accelerated to a much more refined and difficult level.
From the summary in Wikipedia:
Ender plays a game very similar to the Battle Room, where he commands ships in a 3-D space battle simulator. His subordinate officers are fellow students advanced early from the battle school who later become known as "Ender's jeesh". Each day the games become increasingly grueling, and Ender is slowly worn down to exhaustion. Waking and sleeping blend together as Ender nearly loses his mind, while still maintaining his military innovation and leadership. During his restless sleep he has recurring dreams of a fantasy game he played early in his training, as well as visions of the Buggers vivisecting him and removing his memories.
Ender's "final exam" consists of a scenario where bugger ships outnumber Ender's fleet a thousand to one near a planetary mass. Ender orders the use of a special weapon, the Molecular Disruption Device, against the planet itself, destroying the simulated planet and all ships in orbit. Ender makes this decision knowing that it is expressly against the respectable rules of the game, hoping that his teachers will find his ruthlessness unacceptable, remove him from command, and allow him to return home.
Soon after Ender's destruction of the "simulated" Formic fleet, Rackham tells him that all the simulations were real battles taking place with real fleets, and that he had killed all the queens on their home planet. After Ender realizes that he is responsible for the destruction of an entire species (as well as the "simulated" I.F. pilots with which he was careless at times), the guilt of the xenocide sends him into depressive sleep. He also learns at this point that he had previously killed two humans, Bonzo Madrid and Stilson, which only adds to his depression.
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I expect these young drone operators -- especially those operating missiles -- to join the thousands of Army soldiers who have been mentally damaged by the reality of war.
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