What was it that transformed the United States Marine Corps from a quasi-constabulary in 1861 to one of the world's elite fighting forces by 1918? As there was nothing terribly unusual about the Corps' organization or bureaucracy, the only conclusion left is that it must have been its extraordinary people. The Civil War attracted to the USMC a handful of young men who were natural leaders. These men then trained another cohort of talented, tenacious...