"Before 1862, Joshua Lawrence Chamberlain had rarely left his home state of Maine, where he was a trained minister and mild-mannered professor at Bowdoin College. His colleagues were shocked when he volunteered for the Union army, but he was undeterred and later became known as one of the North's greatest heroes: On the second day at Gettysburg, after running out of ammunition at Little Round Top, he ordered his men to wield their bayonets in a desperate...