Last spring, 155 years after the fall of Richmond, the Confederate capital surrendered again. In April 1865, the capitulation was swift and almost outlandishly theatrical: after learning that Robert E. Lee’s army had withdrawn from nearby Petersburg, the Confederate president, Jefferson Davis, and his military guard escaped south under cover of darkness, setting half the city on fire as they fled. Early the next morning, the first Union troops arrived. As Richmond’s black residents celebrated in the streets—joined by more than a few poor whites—the black soldiers at the head of the Union column worked to put out the flames.…