When he outlined America's defense perimeter in Asia and the Pacific at a press conference held fifty years ago today, Harry Truman's leftish Secretary of State Dean Acheson not only left out South Korea, but he indicated that we would not come to the defense of "other areas" in the region (including, presumably, South Korea), should they come under attack. Six months later, North Korea's Communist regime invaded South Korea, and the US once again found itself at war.
For the past half century, historians have debated over whether Acheson's "Perimeter" speech gave North Korea the green light to launch the Korean War.