In 1917, the year the United States entered the Great War, Colonel Moorhead C. Kennedy, one of the most powerful men in the state of Pennsylvania and now the Deputy Director General of Transportation for the American Expeditionary Force, asked his African American valet if he would like to accompany him on an overseas mission. The valet's reaction was "Yes, sir." And he, as he recounted years later, "at once had visions of France." So began Royal Christian's odyssey in Europe. After a tumultuous crossing of the Atlantic as a third class steward on board a British steamship, he survived...