Like many young idealists, Eric Greitens wanted to make a difference, so he travelled to the world's trouble spots to work in refugee camps and serve the sick and the poor. Yet when innocent civilians were threatened with harm, there was nothing he could do but step in afterward and try to ease the suffering. In studying humanitarianism, he realized a fundamental truth: when an army invades, the weak need protection. So he joined the Navy SEALs and became one of the world's elite warriors. Greitens led his men through the unforgettable soul-testing of SEAL training and went on to deployments in Kenya, Afghanistan, and Iraq, where he faced harrowing encounters and brutal attacks. Yet even in the deadliest combat situations, the lessons of his humanitarian work bore fruit. At the heart of this powerful story lies a paradox: sometimes you have to be strong to do good, but you also have to do good to be strong. The heart and the fist together are more powerful than either one alone.