“Ender’s Game” opens Friday in Madison at Point, Eastgate, Star Cinema and Cinema Cafe. PG-13, 1:54, three stars out of four.

“Children in the flower of youth,
Heart in heart, and hand in hand,
Ignorant of what helps or harms,
Without armor, without arms,
Journeying to the Holy Land!”

–Henry Wadsworth Longfellow, “The Children’s Crusade”

“Ender’s Game” knows that if you want to find the most cunning, ruthless sociopaths around, look no further than your local middle-school cafeteria. In the future Earth depicted in Orson Scott Card’s 1985 novel, an International Fleet worried about war with a insect-like alien species turn to super-gifted children to become the next military commanders. The reasoning is that children have strong young minds that can be trained in the ways of strategic thinking, but lack the moral development to worry about the consequences of those actions.

In a movie concerned with tactics and battle formations, “Ender’s Game” is really a Trojan Horse. It enters the theater disguised as a shiny sci-fi action film, only to reveal itself as an old-fashioned morality play about the war for one young boy’s soul.

That boy is Ender Wiggin (Asa Butterfield), the brightest of his class. His older sister (Abigail Breslin) flunked out of Command School for being too soft, his older brother (Jax Pinchak) flunked out for being too aggressive, but the gruff Colonel Graff (Harrison Ford) sees Ender as just right. Graff coldly manipulates Ender so that he’s emotionally isolated from the rest of the students, forced to rely on his own wits. When Ender is attacked by a bully, Ender doesn’t just put him down, he kicks him over and over, sending a message to the other bullies that he’s not to be trifled with. Graff nods approvingly. Ender understand not just war, but pre-emptive war.

Gavin Hood’s film follows Ender’s rapid rise through the ranks, as he strategizes both in zero-gravity combat training and barracks politics to become the natural leader of the other students. Ender learns not only how to lead, but to become comfortable with the idea of sacrificing teammates in pursuit of victory. All the while, Graff watches, approvingly, as the more nurturing Major Anderson (VIola Davis) looks on worriedly. And we wonder just exactly what kind of war Graff is preparing Ender for.

The militarized Earth depicted in “Ender’s Game” doesn’t feel that far off from the one Paul Verhoeven satirized in “Starship Troopers,” and the film offers a similar queasiness about its supposed “good guys.” There hasn’t been an alien attack on Earth in 50 years, and yet the planet is on a perpetual war footing, the airwaves filled with propaganda, “Never Forget” posters on the walls. And the film keeps us guessing about the true nature of the Formic insect race that supposedly poses such an imminent threat. Draw your own War on Terror references here (although I’m guessing Card, who turned into quite the right-wing reactionary since “Game” was published, would rather you didn’t.)

The visual effects in “Ender’s Game” are beautiful but sterile; anyone expecting “Star Wars”-like thrills will be sorely disappointed. The real struggle is taking place behind Butterfield’s blue eyes, as he tries to find a place for his own humanity within Graff’s brutal training. Some of the philosophizing is a little clunky, and the ending offers Ender something of a cop-out, but the film raises real questions about the wisdom of turning young men into killing machines. After all, Ender is only six or seven years younger than 18-year-old Americans who actually do go off to war.

Some have already compared “Ender”s” to sort of a sci-fi “Harry Potter,” with its anointed hero going to school and learning to harness the immense power within him. Maybe in its structure that’s true. But there’s an unsettling undercurrent to “Ender’s Game,” a questioning of the entire process, that makes it a very different experience to watch, as if Harry started wondering if Voldemort was such a bad guy after all.