Do Japan and South Korea Need Nuclear Weapons?

Trilateral meeting
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The North Korean regime of Kim Jong-un conducted its sixth underground nuclear test early this September – which Pyongyang claims as its first test of a hydrogen bomb – and in late August and again, two weeks later, the hermit kingdom launched a ballistic missile directly over the territory of Hokkaido in northern Japan. Now, the U.S. and its key allies in the region – primarily South Korea and Japan – look ahead to the anniversary of the founding of North Korea’s communist party on October 10, which may yield yet another nuclear provocation from the rogue state.

For both Tokyo and Seoul, the nuclear threat posed by North Korea is undeniable, yet neither Japan nor South Korea – rich and technologically capable developed countries – possesses their own nuclear deterrent against Pyongyang or the long term threat posed by rising Chinese military power in the region. The reasons for this are varied, but at the end of the day, one stands out: The U.S. nuclear umbrella. For both countries, the reassurance of the United States that it will retaliate in kind to a nuclear attack on either ally is the lynchpin holding them back. However, as Pyongyang closes in on developing an intercontinental ballistic missile (ICBM) capable of delivering a nuclear weapon to the U.S. mainland, some wonder whether Washington would really be willing to trade Los Angeles for Seoul in a shooting war.

If North Korea does develop a functional nuclear ICBM, could South Korea and Tokyo consider developing their own nuclear deterrent, and what ramifications could that have on regional stability?

Beyond the security of the U.S. nuclear umbrella, there are significant political and historical factors preventing America’s two primary east Asian allies from developing their own deterrent, particularly in Japan. The nuclear bombings of Hiroshima and Nagasaki during World War II showed the Japanese people in livid detail the horrors of nuclear war. As a result, says Kuni Miyake, President of the Foreign Policy Institute in Tokyo, voters have developed a “nuclear allergy based on the experience of Hiroshima and Nagasaki.” This “allergy” played a major role in the creation of a powerful peace movement in Japan and contributed strongly to the strength of the Anpo Toso – protests against the mutual security treaty with the U.S. in 1960, which became the largest mass movement in modern Japanese history and upended the ruling government. In Miyake’s mind, this anti-nuclear sentiment, combined with the budgetary cost of developing and maintaining nuclear weapons, means that “Japan is not likely to go nuclear as long as the U.S. extended deterrence is guaranteed.”

However, says Thomas Cynkin, a former U.S. diplomat in Japan, this is only part of the story. While the development of a Japanese nuclear capability is certainly deeply unpopular, “Japanese leaders have also preserved Japan’s nuclear option both by carefully and consistently articulating their policy in this regard, and by nurturing Japan’s actual capacity to produce and deploy nuclear weapons.” The Anpo Toso protests in 1960 largely nixed the plans of then Prime Minister Nobosuke Kishi – current Prime Minister Shinzo Abe’s grandfather – to rearm Japan after the war and possibly develop an independent nuclear capability. However, Japanese policymakers have never fully left nuclear weapons off the table. Instead, they have cultivated a nuclear “latency option,” while pursuing a strictly non-nuclear official policy. Boasting an advanced civilian nuclear industry, Cynkin says the country is estimated to have “9 tons of plutonium, enough for over 1,000 warheads,” as well as an advanced space industry, which provides easy access to ballistic missile technology. The end result is a non-nuclear Japan with the capability to rapidly become nuclear if the U.S. guarantee is undermined.

These dynamics are quite different in South Korea. There, the concept of developing a domestic nuclear capability is far more openly discussed, especially as North Korea’s nuclear program accelerates. According to a Gallup Korea poll, 60 percent of South Koreans support developing their own nuclear capability, while 68 percent want to see U.S. nuclear weapons, which were removed from the peninsula by President George H.W. Bush in 1991, redeployed there. In fact, says Admiral James ‘Sandy’ Winnefeld, Cipher Brief Expert and former Vice Chairman of the Joint Chiefs of Staff, as recently as August 2004, “Seoul owned up to the International Atomic Energy Agency (IAEA) to having done some nuclear weapons research.” In addition, experts believe South Korea could develop its own nuclear arsenal in as little as 18 months.

There are several key factors holding Seoul back, however. First, if South Korea develops its own nuclear arsenal it would have to leave the NPT, this would put it in league with North Korea, which withdrew in 1993. In addition to this diplomatic dent to South Korea’s reputation, an independent nuclear deterrent could prompt other regional powers – including Japan – to develop their own capabilities. More importantly, it would almost certainly provoke an aggressive reaction from Pyongyang and China, and it would alienate the United States, which insists that the security of South Korea is guaranteed under the nuclear umbrella and has strongly pressured South Korea to remain non-nuclear throughout its history.

For these reasons, it is unlikely that the South Korean government, and especially its relatively pacifist President Moon Jae-In, would pursue their own capability in the near future. Instead, says Winnefeld, hints “from a nation like South Korea that they are considering developing their own weapon would…likely stimulate further reassurances that they do not need to because we have their back…it is possible that such hints are merely designed to gain such reassurance.”

This strategy is very close to what Cynkin describes as Japan’s “policy of preserving a latent nuclear option” as a means to keep the United States nuclear guarantee rock solid. After a period of uncertainty in the early days the Trump Administration about the U.S commitment to its east Asian alliance system – during the presidential campaign Trump said that U.S. allies should pay more for their security and suggested that Japan develop its own nuclear weapons – American security assurances now seem to be on better footing. In June, for instance, Trump promised to protect South Korea with “the full range of United States military capabilities, both conventional and nuclear.”

This is a positive sign. The possibility of either Seoul or Tokyo developing their own nuclear arsenals would both deeply strain their alliances with the United States and dangerously provoke North Korea and China. However, a North Korea ICBM capable of reaching the United States will almost certainly bring this issue back to prominence. If that capability is real, it means that a decision to retaliate against North Korea for an attack on South Korea, Japan, or any other U.S. ally would risk the destruction of an American city. When that happens, the Trump Administration will need to make sure that its nuclear guarantee is reliable if it wants to prevent its east Asian allies from considering their own nuclear options.

Fritz Lodge is an analyst at The Cipher Brief. Follow him on Twitter @FritzLodge.

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