After the Communist Party took power in mainland China in 1949, following a brutal civil war, the Nationalist government fled to Taiwan. But Beijing viewed the island as part of its territory, and the two sides clashed intermittently over the following decades.

According to the leaked documents, some US Defense and State department officials were concerned the loss of the outlying islands in 1958 could lead to a full "Chinese Communist takeover of Taiwan."

In the event of an air and sea attack on the islands, US Air Force Gen. Nathan Twining said the US would have to use nuclear weapons against Chinese air force bases "to prevent a successful air interdiction campaign," beginning with "low-yield ten to fifteen kiloton nuclear weapons."

If this didn't lead to a break in the assault from mainland China, "the United States ... would have no alternative but to conduct nuclear strikes deep into China as far north as Shanghai."

According to the documents, the Chairman of the Joint Chiefs acknowledged this would "almost certainly" lead to nuclear retaliation against Taiwan and the US military base at Okinawa in Japan. "But he stressed that if national policy is to defend the offshore islands then the consequences had to be accepted," the document said.

Given China had yet to develop its own nuclear capabilities, any nuclear retaliation would have come from the Soviet Union, possibly sparking an even more devastating global conflict. The report said it isn't clear where the nuclear retaliation would have originated.

The document said the US Joint Chiefs, and Twining in particular, saw the use of atomic weapons as "inevitable." In one section, Gen. Laurence S. Kuter, the top Air Force commander for the Pacific, "flatly" states that any US air action against a Chinese attack on the outlying islands "had no chance of success unless atomic weapons were used from the outset."

"It's no surprise the White House said no," he said.

A ceasefire was reached in the Taiwan Strait on October 6, 1958, although there have been ongoing tensions between Beijing and Taipei.

Beijing claims full sovereignty over Taiwan, a democracy of almost 24 million people located off the southeastern coast of mainland China, even though the two sides have been governed separately for more than seven decades.

With military tensions rising again between the US and China, whistleblower Ellsberg said in his interview with the Times that he had supplied the documents due to his concerns over the possibility of a new war over Taiwan.

"Note to @JoeBiden: learn from this secret history, and don't repeat this insanity," he said.