One of the darkest periods in American military history began on June 25, 1950, when hordes of North Korean troops stormed across the 38th Parallel into South Korea. The Communists' blitzkrieg-style invasion came less than five years after the end of World War II, when the United States had owned the world's mightiest war machine, but it caught a carved-down, ill-equipped U.S. Army woefully unready.