JFK’s Forgotten Crisis: Tibet, the CIA and the Sino-Indian War. By Bruce Riedel. Brookings Institution Press; 256 pages; $29.

IN THE autumn of 1962 Chinese troops invaded Indian-held territory, attacking across the 1,800-mile (2,880km) border that stretches along the Himalayas between the two giants of Asia. Mao Zedong instructed his army to expel Indian soldiers from territory that China claimed in Kashmir. In Washington the Chinese offensive was seen as a serious communist move in the cold war.

It was an inconvenient moment for the White House. President John Kennedy was absorbed in an even bigger crisis with communism closer to home: the flow of Soviet missiles to Cuba which threatened a nuclear conflict. Luckily for Kennedy, he had his own man in New Delhi. His friend from Harvard, John Kenneth Galbraith, was the American ambassador. So in a relatively easy act of delegation, Galbraith was put in charge of the “other” crisis.

Galbraith proved up to the task, in part, as Bruce Riedel writes in “JFK’s Forgotten Crisis”, because he had access to the president and his aides. Most ambassadors report to the State Department, but the blunt Galbraith told the president that going through those channels was “like trying to fornicate through a mattress”.

The border war did not last long. The Chinese crushed the Indians. Mao declared a unilateral ceasefire a month later and withdrew Chinese forces. He had prevailed over his Asian rival, humiliating the Indian prime minister, Jawaharlal Nehru.

But victory was not just about Chinese might. At Galbraith’s urging, the Americans had quickly backed the distressed Nehru. An emergency airlift of supplies was sent to Calcutta and a carrier battle group was dispatched to the Bay of Bengal. In the end, Mao judged that the Americans might actually come to the help of India. He did not want to suffer huge losses of Chinese soldiers so soon after the Korean war. Thus American deterrence worked, and a confrontation between America and China was avoided, Mr Riedel writes.

The actual war is just one facet of this high-wire story of the geopolitics of the period, with its outsized characters and decisions that still reverberate today. Mr Riedel puts his experience as a former CIA analyst and a senior adviser on the National Security Council to canny use, uncovering details about an American covert operation in Tibet that has been mostly forgotten, though not by China.

Between 1957 and the early 1970s America spirited young Tibetans out of their homeland through Bangladesh (then East Pakistan), trained them in Colorado, and parachuted them back into Tibet, where they fought the Chinese army. Galbraith described the covert effort as “a particularly insane enterprise”. But the CIA prevailed. In 1961 the Americans were so starved for information about China that the CIA bragged about the ambush of a Chinese army truck by the Tibetan rebels. Mr Riedel describes how a bloodstained satchel of Chinese documents from the truck was taken to the White House as prized bounty. The Americans were so ignorant about the early years of communist China, he writes, that the operation was deemed worth the risk because of the documents’ descriptions of the status of Sino-Soviet relations, and the grim conditions in the Chinese countryside.

The current alliances on the subcontinent and the unsettling arms race between Pakistan and India hark back to the war of 1962. Kennedy’s decision to help India drew Pakistan closer to China. India started down its path to becoming a nuclear power after its defeat by China. When India tested a nuclear weapon in 1998, the rationale was the threat from China.

Today China and India are competitors, not enemies. But more than 50 years after the war, the border dispute remains unresolved. The two countries account for more than a third of the world’s population. In July 2014 at the first meeting between the Chinese leader, Xi Jinping, and Narendra Modi, India’s prime minister, Mr Xi said: “When India and China meet, the whole world watches.” This superb history shows why.