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When I was younger (early 2000s), I read a young adult novel about a post-apocalyptic earth where the people live in small domed cities because of nuclear fallout and play war games to decide who owns any new clean land.
The main character has been bred to be the best at the game. He has the power to detect the magnetic field of the board pieces which is a requirement to play. He loses his powers for some reason but then wins anyways because his country or teammate cheats and then goes and lives on the island that he won.