When God first visited him in 1857, Oliver Otis Howard was a lonely army lieutenant battling clouds of mosquitoes in a backwater posting that he described as a “field for self-denial”: Tampa, Florida. Howard had spent his life swimming against powerful tides. Ten when his father died, he had to leave his family in Leeds, Maine, and move in with relatives. Through constant study, he made it to Bowdoin College at age 16, graduating near the top of his class …