The Inevitable Logic of a Japanese Nuclear Weapon

In democracies, security policy must rest on a foundation of public support. Such a foundation does not yet exist in Japan on the nuclear question. It is therefore imperative that Japan engage in an open, realistic, and timely public debate to build a national consensus on this vital issue. Japanese Prime Minister Sanae Takaichi took a first step in this direction earlier this month, when she announced that her government is considering a review of Japan’s long-standing policy on hosting nuclear weapons.

It is no longer a question of if but when Japan and South Korea will acquire independent nuclear deterrents within the U.S. alliance system. That system would otherwise loosen in East Asia as the United States’ extended deterrence—the so-called nuclear umbrella—erodes due to China’s and North Korea’s acquisition of second strike capabilities targeting the U.S. mainland. To acquire nuclear weapons will be a politically difficult and highly fraught decision—much more so for Japan than for South Korea, where opinion polls already show considerable support. But regardless of public opinion, changes in the global and regional strategic environment are inexorably pushing both countries in this direction. Resisting the logic of these changes could lead to very grave geopolitical consequences.

It is no longer a question of if but when Japan and South Korea will acquire independent nuclear deterrents within the U.S. alliance system. That system would otherwise loosen in East Asia as the United States’ extended deterrence—the so-called nuclear umbrella—erodes due to China’s and North Korea’s acquisition of second strike capabilities targeting the U.S. mainland. To acquire nuclear weapons will be a politically difficult and highly fraught decision—much more so for Japan than for South Korea, where opinion polls already show considerable support. But regardless of public opinion, changes in the global and regional strategic environment are inexorably pushing both countries in this direction. Resisting the logic of these changes could lead to very grave geopolitical consequences.

In democracies, security policy must rest on a foundation of public support. Such a foundation does not yet exist in Japan on the nuclear question. It is therefore imperative that Japan engage in an open, realistic, and timely public debate to build a national consensus on this vital issue. Japanese Prime Minister Sanae Takaichi took a first step in this direction earlier this month, when she announced that her government is considering a review of Japan’s long-standing policy on hosting nuclear weapons.

The peculiarity of nuclear strategy—for Japan as for anyone else—is that it is almost entirely based not on experience but on abstract logic. Nuclear weapons have only been used twice in war—and only under circumstances that are unlikely to occur again. Despite a close call during the 1963 Cuban missile crisis and the more recent nuclear saber-rattling by Russia over its war in Ukraine, no one has any practical experience of the use of nuclear weapons in the 80 years since the attacks on Hiroshima and Nagasaki.