Excerpts from Destabilizer-in-Chief by Mario Loyola in National Review:

The Korean War is justly remembered as a valiant struggle. And yet the conflict could have been avoided but for a major blunder on the part of the Truman administration. The year before South Korea was attacked, the U.S. withdrew the forces it had left there in the wake of World War II. It was the ensuing vacuum of power that precipitated that terrible war.

The lesson has been lost on most Americans, starting with Barack Obama. Bent on withdrawing U.S. power from the Middle East, Obama removed the major counterweight to the competing extremist forces there. As a result, the conflicts smoldering beneath the surface have burst into a major conflagration in a region that is far more vital to U.S. interests than Korea was.

When the U.S. withdrew its forces from Korea in the spring of 1949 — against the advice of commanders on the ground — it left behind a lightly armed dictatorship in no condition to defend itself. And then, in January 1950, Secretary of State Dean Acheson delivered his famous “perimeter speech,” which pointedly left South Korea outside our postwar military perimeter along the Pacific Rim.

It was an irresistible invitation for the North to invade, and when Kim Il-sung accepted it in June 1950, he bulldozed over the South’s army and rapidly engulfed most of the country. The Truman administration reacted quickly, and American forces began pouring into the vanishing redoubt in Pusan, at the southeastern tip of the peninsula.

Somebody should have pointed out to Truman in 1949 that, having withdrawn the garrison and left South Korea a sitting duck, he had made a North Korean invasion much more likely. If the U.S. was prepared to fight in Korea, it should have left sufficient forces there to deter an attack in the first place. Bolstering a dictatorship like Syngman Rhee’s was hardly palatable, but we ended up having no choice.

U.S. forces in Korea eventually reached 330,000 troops. And, in a horrific irony, the number of U.S. soldiers killed or missing in action proved almost exactly the same as the number we withdrew in 1949. In many cases the Americans who died in Korea were the same soldiers we had withdrawn to Japan a year or two earlier. Little did they know that, by being withdrawn from Korea too soon, they were being sent to their graves.