In August 1943, at the height of the Second World War, LIFE magazine published a lengthy article titled, "Negro Division." The racial tensions that have inexorably shaped American history and, in large part, defined American culture have rarely been more urgent or widespread than they were at that moment, when U.S. troops were "fighting for freedom" overseas while codified prejudice and legislative inequality remained in force throughout the United States. In fact, just months before the article appeared in LIFE, a massive race riot tore through Detroit, leaving dozens dead, hundreds injured and thousands -- mostly African Americans -- under arrest.
LIFE's "Negro Division" article, meanwhile, chronicled and (somewhat mutely) celebrated the increasing number of black troops in American combat units, focusing primarily on one unit: the famed 93rd Infantry Division, its 16,000 enlisted men and its thousand officers -- half of whom were African American -- training at Fort Huachuca in Arizona.
Here, LIFE.com looks back at a pivotal moment in American history, when many thousands of citizens, men and women, were training to fight for and otherwise defend a country that had long resisted the very notion of "liberty and justice for all." There's more than heroism in that sort of effort; seen in a certain light, there's a kind of radical optimism that, in the end, defines the imperfect, audacious American experiment as well as anything ever has.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.