... As global anxiety mounts, remedial history is in order.

In the summer of 1950, when North Korea started the Korean War with Soviet backing, Kim Il-sung was just 38 years old — a willful, pugnacious, wet-behind-the-ears dictator, not unlike his grandson today. In secret meetings with Stalin before the invasion, Kim delivered wildly enthusiastic and laughably wrongheaded analyses of how the war would unfold when his army stormed into South Korea.

He predicted that a formidable pro-Communist guerrilla force would spontaneously rise up in the South to fight with the North Korean military. It did not. He promised that the South Korean people would rally round his leadership. They did not. To top off his dubious claims, Kim assured Stalin that a North Korean victory would come in three days and the Americans would not intervene. The war has never ended; Americans still patrol the DMZ.

At his dacha outside Moscow, Stalin didn’t completely buy what Kim was trying to sell. He warned his eager Korean acolyte, “If you should get kicked in the teeth, I shall not lift a finger.” But the old Soviet boss wanted to torment the United States. So, he approved and supplied the invasion, while ordering Kim Il-sung to make it look as if South Korea had started the war.

The United States, of course, did fight back. President Harry S. Truman, Congress and the public were outraged by the invasion, interpreting it as a challenge to America’s character. In less than a week, Truman approved the use of ground forces.

After a halting and discouraging start that cost the lives of thousands of G.I.s, the American war machine became a murderous, unstoppable force. Using bombs and napalm, the United States Air Force blew up and burned down virtually every population center in North Korea. Gen. Curtis LeMay, head of the Strategic Air Command during the Korean War, estimated that “over a period of three years or so, we killed off — what — 20 percent of the population.” That’s about 1.9 million people.

American troops — fighting with South Korean and United Nations forces — shredded North Korea’s invading army, occupied Pyongyang, and marched north to the Chinese border, effectively erasing North Korea. Mao Zedong then stepped in, unwilling to tolerate American soldiers on his doorstep. Mao’s top general, Peng Dehuai, quickly sized up Kim Il-sung as a battlefield nincompoop. Calling his leadership “extremely childish,” Peng elbowed Kim out of the chain of command and made him a helpless spectator to his own war. Vast numbers of Chinese troops died to save North Korea from Kim’s bloody mistake; they kept his regime from becoming a footnote in Asian history. ...