Did Tokyo secretly allow US warships carrying nuclear weapons to dock in Japanese ports during the Cold War?

Shinobu discovered the documents in the United States National Archives and Records Administration and the National Security Archive. They cover negotiations from 1958 to 1960, primarily involving Japanese Foreign Minister Aiichiro Fujiyama and U.S. Ambassador Douglas MacArthur, who presided over Japan's surrender during World War II and was the country's de facto leader from 1945 to 1951.

In February 1958, Prime Minister Nobusuke Kishi addressed the Diet, stating that Japan would not allow the United States to introduce nuclear weapons into Japan or its territorial waters. This policy would effectively nullify the previous tacit agreement with Washington, leaving the United States at a military disadvantage relative to the Soviet Union in the Pacific.

MacArthur was tasked with finding a way to circumvent Kishi's promise to the Japanese people and keep nuclear weapons aboard warships docked at American bases in the country.

“The US needed this agreement to allow the US military to operate as it did before the revisions to the Japan-US security treaty,” Shinobu told This Week in Asia.

“In other words, American ships were carrying nuclear weapons on board to Japan and wanted to continue to do so after the security treaty was revised.

“Japan agreed to the US request because it was in a weak negotiating position,” Shinobu said. “It was the Japanese side that wanted the treaty revised, and they had to achieve this at all costs.”

The solution was that the revised security treaty – signed on January 19, 1960 – contained a clause allowing American warships to continue entering Japanese ports without first informing Japanese authorities that they were carrying nuclear weapons.

The clause was kept secret – despite deep concerns on the Japanese side that if news of the deal were leaked, it could prove fatal for Kishi's government as it would directly contradict the prime minister's promise to the Diet. Shinobu thinks the administration “probably would have collapsed.”

“The Japanese people and the Socialist Party, as well as others, questioned whether the Seventh Fleet carried nuclear weapons on board. Once it became evident, I don't think the government could have explained it,” he said, adding that such political unrest would also have deteriorated the country's security relations with Washington.

James Brown, a professor of international relations specializing in Russian affairs at Temple University's Tokyo campus, said Japan still suffers from a “nuclear allergy,” with the atomic bombings of Hiroshima and Nagasaki still fresh in memories.

“In the 1950s, public opinion was very strong against anything to do with nuclear weapons and although Japan was essentially in agreement on the subject, the government of the time felt it was so sensitive that it had to remain secret,” he said. .

He acknowledged that a leak revealing that Kishi had lied and approved the U.S. military's nuclear weapons in Japanese waters would have led to his resignation, even though the dominant Liberal Democratic Party would likely have replaced him with another politician from the PLD and would have moved on.

Stephen Nagy, a professor of international relations at the International Christian University in Tokyo, said the Kishi government ultimately had no choice but to comply with Washington's wishes.

“Japan claims to have three firm non-nuclear principles, but they are ironically protected by the US nuclear umbrella,” he said. “This position is understandable and pragmatic, but remains contradictory.”

The current Japanese government still adheres to these same principles, Shinobu said, although they are not legally binding and are more akin to national policy. And the question is moot at the moment, he added.

“After the end of the Cold War, President George Bush Sr. decided that no nuclear weapons would be carried on ships in peacetime,” he said. “The U.S. government also emphasizes Japan's three non-nuclear principles, so ships carrying nuclear weapons are unlikely to call at Japanese ports during peacetime.”