By late 1950 Kim Il Sung had been routed. Four months after his army invaded the South, the North Korean leader had fled his capital of Pyongyang as American-led U.N. forces pressed toward the border of the newborn People's Republic of China. Within a few weeks, though, Chinese "volunteers" poured into Korea and turned the tide of war, prolonging it for 2 1/2 years and keeping Kim's communist stronghold intact.
What happened? For many years, historians believed that Stalin had given Mao Zedong marching orders. Now comes the first official evidence that Mao acted on his own in the interests of...