Top U.S. military officials considered giving the Self-Defense Forces atomic weapons in the 1950s under an arrangement similar to NATO’s “nuclear-sharing” deal, declassified documents from the U.S. Joint Chiefs of Staff revealed Friday.

In February 1958, the Joint Chiefs decided its “position,” saying: “The United States would prefer that Japan integrate appropriate atomic weapons into the Japanese self-defense forces.”

The decision came five months after the U.S. military and the SDF conducted a joint map exercise assuming the use of nuclear weapons, according to the documents.

The nuclear map exercise, conducted in September 1957, had never been revealed to the public until a joint investigation by Kyodo News and Akira Kurosaki, an associate professor of Fukushima University, uncovered the documents recently at the U.S. National Archives in Maryland.

As Cold War tensions rose in the 1950s with the Soviet Union’s successful nuclear tests and its development of hydrogen bombs, the administration of President Dwight D. Eisenhower dramatically increased its dependence on nuclear arms under its “New Look” policy, which equated them with conventional weaponry.

The Joint Chiefs decision on a potential nuclear option for Japan — which had been attacked with atomic bombs just a decade earlier — is consistent with the idea that U.S. Cold War mentality relied on nuclear arsenals as a countermeasure against the massive conventional capability of the Soviet bloc.

A document, dated Feb. 17, 1958, said that “combined U.S.-Japan Map Exercise FUJI was conducted in Japan during the period 24-28 September 1957,” during which the use of nuclear weapons was simulated.

Although the document does not give a specific venue for the exercise, an oral record by a former senior Ground Self-Defense Force official, the late Gen. Ryuhei Nakamura, indicated that “FUJI” was held at Camp Drake, a U.S. base that was once located in an area straddling Tokyo and Saitama Prefecture.

The record was left at the National Institute of Defense Studies, a research branch of the Defense Ministry.

According to the oral record, the Japanese participants wanted to know how the U.S. military would use tactical nuclear weapons in Japan. The U.S. side, however, did not provide precise information.

Still, the Joint Chiefs documents detailed questions raised by the Japanese “co-director” during the joint map exercise.

“Would the United States hold all the nuclear weapons for use by her own delivery systems or would the United States release some weapons for use by Japan?” the document paraphrased the questions posed by the co-director.

According to the paper, the co-director also asked if the U.S. would “prefer Japan to have conventional weapons only,” while also querying the sensitive issue of whether Washington would give its blessing for Tokyo acquiring atomic weapons.

“If Japan were to decide to arm herself with nuclear weapons, could she depend upon U.S. support for such a plan?” the document said.

A memorandum dated Nov. 20, 1957, by Chief of Naval Operations Adm. Arleigh Burke said “the significance of the questions posed by the Japanese Co-Director . . . warrants the early consideration of the Joint Chiefs of Staff.

“These questions express the concern of the only country in the world that ever experienced a nuclear attack . . .” the memorandum added.

In response to Burke’s suggestion, the Joint Chiefs ultimately decided its positions at a meeting on Feb. 12, 1958.

The Joint Chiefs document dated Feb. 17, 1958, further elaborates on its positions, saying “(t)he provision of such weapons support to Japan would be primarily dependent on the desires of Japan to be provided with atomic weapons and her development of capability to employ effectively such weapons.”

In addition to the U.S. preference for integration of nuclear weapons with the SDF, the Joint Chiefs document said, “(the SDF) must eventually be equipped with the most modern conventional and atomic weapons.”

These Joint Chiefs positions were conveyed to the Commander-in-Chief, U.S. Pacific Command (CINCPAC).

Another Joint Chiefs document dated Sept. 17, 1958, noted “(t)he United States is willing to support her allies with atomic weapons, after the NATO pattern, subject to the desire of Japan to acquire such weapons and to develop a capability for their effective employment.”

However, the Joint Chiefs positions on arming the SDF with nuclear weapons were not formally proposed to the Japanese government.

Other declassified U.S. documents obtained by Kyodo News suggested caution by U.S. policymakers who were familiar with Japan’s volatile domestic situation and growing anti-nuclear sentiment following the March 1954 Daigo Fukuryu Maru (Lucky Dragon No. 5) incident, in which a Japanese fishing vessel was exposed to radioactive fallout from the U.S. thermonuclear “Bravo Shot” near the Bikini Atoll in the Pacific.

“The U.S. military considered integration of nuclear weapons into the SDF, and some SDF officials showed interest in this idea,” Fukushima University’s Kurosaki said.

“There was a backdrop that the U.S. administration deepened its dependence on nuclear weapons in its national security strategy. From these contexts, then-Prime Minister (Nobusuke) Kishi stated it is possible for Japan to possess nuclear weapons (for defensive purposes) even under the Constitution,” he said.

Kurosaki said he wonders if Japan would have continued to be a nonnuclear power if the Daigo Fukuryu Maru incident had not occurred and anti-nuclear sentiment in the country had not risen so sharply.

On the Japanese side, from the mid-1950s to mid-1960s, the Staff College of the Japanese Ground Self-Defense Force taught future top officials about nuclear tactics and doctrines that were imported from the U.S. Command and General Staff College (CGSC), former top SDF officials told Kyodo News.

“Which direction would nuclear fallout move and how should we conduct military operations evading this fallout? These were brought back to Japan by a SDF official who studied (nuclear tactics) at the U.S. CGSC,” former GSDF Major Gen. Kiyoshi Maekawa said.

But nuclear courses at the Staff College in Tokyo were suspended after the public’s growing anti-nuclear sentiment culminated in the government crafting the three nonnuclear principles in 1967.

“The Lucky Dragon Incident, the (national-level) ban-the-nuclear-bomb movement and three nonnuclear principles” greatly impacted the SDF’s position, former Gen. Mitsuaki Yokochi said.

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