U.S. President Barack Obama’s declaration in 2009 of working toward a world free of nuclear weapons was widely praised by Japan, the only country to suffer a nuclear bomb attack.

But officials are tight-lipped about why, behind the scenes, Japanese diplomats were arguing for maintaining the U.S. nuclear deterrence.

Those in a position to know about the Japanese stance back then have either declined to comment or pleaded memory loss when asked why Tokyo chose to remain under the U.S. nuclear umbrella instead of pushing for nuclear disarmament.

In February 2009, the Congressional Commission on the Strategic Posture of the United States heard from a number of Japanese officials, including Takeo Akiba, then a minister with the Japanese Embassy in Washington and now a vice foreign minister.

Those diplomats all stressed the importance of having the United States maintain its nuclear deterrence.

In early May this year, two opposition Upper House members, Yukihisa Fujita of the Democratic Party for the People and Hiroe Makiyama of the Constitutional Democratic Party of Japan, met with Paul Hughes, who served as executive director of the commission.

The two lawmakers asked what the Japanese diplomats had said during the commission hearings.

“The conversation held within the commission are things I cannot speak to because we are obliged not to comment on what was said,” Hughes told them. “It is up to the government (of Japan) to decide if its officials can speak to the media or members of the Diet.”

The lawmakers decided to pursue the issue after Gregory Kulacki, a senior analyst with the Union of Concerned Scientists, revealed during an April visit to Japan that the Japanese officials only argued for maintaining the U.S. nuclear deterrence and said almost nothing about nuclear disarmament.

The Cabinet of Prime Minister Shinzo Abe on April 10 approved an official response that said it would be difficult to go into details about discussions at the commission because of an understanding that the contents would not be divulged outside the hearings.

The response only said that an explanation had been made for the need to secure Japan’s national security under the deterrence provided by the Japan-U.S. Security Treaty.

A few months after the commission heard from the Japanese diplomats, Obama spoke in Prague and pledged to work toward a world without nuclear weapons.

Taro Aso, who was prime minister at the time, called for cooperation in working toward that goal.

As for the Japanese calls for maintaining the U.S. nuclear deterrence at that time, the Cabinet response explained that the diplomats were passing along the thinking of the government after obtaining approval of the foreign minister.

Upper House member Hirofumi Nakasone, who was foreign minister at the time, submitted a written response to The Asahi Shimbun that said he could not recall details of what transpired. He suggested that confirmation be made with the government and Foreign Ministry.

One recommendation made by the U.S. commission was the establishment of a forum for dialogue with Japan about the nuclear issue. That led to the start in 2010 of a panel on extended deterrence, including high-ranking officials from Japan and the United States working on foreign policy and defense.

Bradley Roberts, a staff member of the commission, was one of the officials who pushed for that dialogue panel. He would later be appointed deputy assistant secretary of defense for nuclear and missile defense policy.

Roberts also served as a visiting fellow at the National Institute for Defense Studies in Tokyo. He published an article in 2013 that praised the extended deterrence dialogue forum for dealing with such topics as North Korea’s nuclear weapons and ballistic missile development programs and the modernization of the Chinese military.

Roberts also wrote that future topics for discussion included fine-tuning the U.S. nuclear umbrella to respond to possible threats from not only Russia, but also China and North Korea, as well as how Japan could support that umbrella by strengthening its missile defense and possessing the capability to strike enemy bases.

Japan has in fact beefed up its missile defense. Whether Japan should possess the capability to strike enemy bases is expected to be a key topic in the review of the National Defense Program Guidelines to be completed before the end of the year.