In 1969, China and the Soviet Union seemed on the brink of war. They fought a deadly border clash in March of that year and another in August. The Kremlin dropped hints of a nuclear strike. Over the next few years, they exchanged barbs. Mao Zedong "You piss on my head, and I shall retaliate!” Soviet leader Leonid Brezhnev called Mao “treacherous.” An alliance that Moscow and Beijing previously billed as unbreakable quickly unravelled. So Mao reached out to his avowed foe the United States. Mao, a scathing critic of what he called American imperialism, suddenly referred to President Richard...