Steal Fire from the Gods — Clint Hall

The Human Alliance knew the war was over when the machines started using magic to cast fire, shake the ground, conjure storms, and part the seas.  We fought back anyway. 22-year-old soldier Gunnar Graves lost his faith and his family when a platoon of AI-driven war machines—led by an android fire mage—destroyed his unit. Forced to live in a machine-controlled village and hiding a dark secret, he spends his days trying to learn elemental power so he can take his revenge. After years of failure, his ability ignites when he least expects it. On the run and hunted by the war machines, Gunnar discovers that an ancient, life-based strength has awakened to help humanity fight back. Joined by the other life mages, Gunnar is thrust into a mad world of android overlords, cyborg clans, and evil forces bent on his destruction. To protect his newfound family, Gunnar must discover the truth behind a power he doesn't understand and wage a war he doesn't believe they can win.