The 50 Sectiors

The 50 Sectors. The United States of America have perished, and in their place are the 50 Sectors. War was waged and far too many were killed fighting their own people. Now, with the sectors' populations rising, a system is created. From each sector, one girl and one boy are picked at random from the ages of 12 to 20 and tested in a multitude of ways: mentally, physically, emotionally, and genetically. Whichever cadets manage to pass all of these stages, they are kept and trained, forced into an elite program, whilst anyone who fails one or more are killed. Dead.
The program is beyond intense. You're trained to fight, handle weapons, and strategize to perfection. Trained to be emotionless and heartless, only showing emotions when they are needed for a job. Trained to be fearless and near indestructible. They become the government's playthings. Those who succeed are sent off as spies and soldiers to other countries that took part in killing the U.S. to do the same thing to them.
These are the 50 Sectors.