Shadow of the Hegemon (The Shadow Series)

The War is over, won by Ender Wiggin and his team of brilliant child-warriors. The enemy is destroyed, the human race is saved. Ender himself refuses to return to the planet, but his crew has gone home to their families, scattered across the globe. The battle school is no more. But with the external threat gone, the Earth has become a battlefield once more. The children of the Battle School are more than heroes; they are potential weapons that can bring power to the countries that control them.