Rough Crossings turns on a single huge question: if you were black in America at the start of the Revolutionary War, whom would you want to win? In response to a declaration by the last governor of Virginia that any rebel-owned slave who escaped and served the King would be emancipated, tens of thousands of slaves -- Americans who clung to the sentimental notion of British freedom -- escaped from farms, plantations and cities to try to reach the British camp. This mass movement lasted as long as the war did, and a military strategy originally designed to break the plantations of the American South had unleashed one of the great exoduses in American history.