Robert Einhorn on South Korea’s Nuclear Weapon Development

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Robert Einhorn on South Korea’s Nuclear Weapon Development

“If North Korea’s nuclear threat continues to grow, the answer is not for the United States to support a South Korean nuclear weapons program.”

Robert Einhorn on South Korea’s Nuclear Weapon Development

An M270 Multiple Launch Rocket System from A Battery, 6th Battalion, 37th Field Artillery Regiment, 210th Field Artillery Brigade, 2nd Republic of Korea/United States Combined Division, fires an MGM-140 Army Tactical Missile into the East Sea, July 5, 2017.

Credit: Sgt. Sinthia Rosario / 5th Mobile Public Affairs Detachment

Since South Korean President Yoon Suk-yeol took office in May 2022, South Korea has aimed to tackle North Korea’s nuclear programs by strengthening its military alliance with the United States. Denouncing his predecessor’s dovish overtures centered on dialogue on North Korea, Yoon vowed to enhance the country’s defense capabilities to ensure overwhelming superiority in a war scenario.

With the North’s resumption of testing various ballistic missile programs – including intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) – South Korea and the U.S. have reinvigorated their joint military drills to effectively respond to the North’s nuclear and missile threats.

Under Seoul’s strong demand to scale up the military drills, Washington has also pledged to utilize the full range of U.S. defense capabilities, including nuclear assets, under the U.S. extended deterrence to defend Seoul from any nuclear attacks. However, the U.S. extended deterrence appears to have failed to stem South Koreans’ desire to acquire their own nuclear weapons.

According to a survey conducted by the Chicago Council on Global Affairs released in February 2022, 71 percent of the respondents supported the country obtaining nuclear weapons, regardless of their faith in the South Korea-U.S. alliance. When asked to choose between developing South Korea’s own nuclear weapons and redeploying U.S. nuclear weapons on South Korean soil, 67 percent supported the country’s own nuclear development, while only 4 percent supported the redeployment of U.S. nuclear weapons.

In other words, after three decades of implementing alternatively dovish and hawkish overtures towards North Korea, most South Koreans now believe possessing nuclear weapons is the most effective means to deter the North’s missile launches.

Proponents of the idea say it’s the only way to guarantee Seoul’s safety amid North Korea’s growing nuclear arsenal; critics counter that it would gut the international non-proliferation regime and deal severe damage to South Korea’s international reputation.

The United States has already made clear that it does not support South Korea’s nuclear development due to its continued emphasis on the “complete, verifiable, and irreversible denuclearization” (CVID) of the Korean Peninsula. Washington also is not considering redeploying tactical nuclear weapons on the Korean Peninsula at this stage.

However, Yoon has not excluded the possibility of his country developing its own nuclear weapons, saying that this option can be considered as the North’s nuclear threat grows.

In this context, the possibility of South Korea going nuclear must be taken seriously – and the potential consequences carefully weighed.

For an in-depth look, The Diplomat’s Mitch Shin conducted an exclusive interview with Robert Einhorn, a senior fellow in the Arms Control and Non-Proliferation Initiative and the Strobe Talbot Center for Security, Strategy, and Technology at the Washington, D.C.-based Brookings Institution.

Einhorn previously served as a special adviser for nonproliferation and arms control in the U.S. Department of State, a position created by then-Secretary of State Hillary Clinton in 2009. Along with his initiatives focused on nonproliferation, he served as U.S. delegation head in negotiations with South Korea on a successor civil nuclear agreement.

What is the United States’ formal position on the idea of South Korea developing its own nuclear weapons? 

The United States has long opposed South Korea’s development of nuclear weapons. That remains the U.S. position, although U.S. officials may be reluctant to state that position forcefully and publicly for fear of appearing to pressure a close ally on a matter affecting its vital interests.

The Biden administration recognizes the acute threat to South Korea’s security posed by the rapid growth of North Korea’s nuclear and missile capabilities. But it believes the U.S.-South Korean alliance already provides a strong deterrent against North Korean aggression – a deterrent consisting of the allies’ combined conventional military capabilities (including South Korea’s powerful conventional forces) and the U.S. commitment to come to the defense of its ally using the full range of its capabilities, including nuclear weapons.

Washington believes that a decision by South Korea to acquire its own nuclear weapons could significantly increase tensions in Northeast Asia, lead other countries to acquire nuclear weapons, and weaken the U.S.-South Korea alliance, which would undermine deterrence against the North.

Is extended deterrence the best policy Washington can implement to defend South Korea from nuclear attacks? 

The Biden administration believes the best approach to addressing the North Korean threat is to rely on a combination of the allies’ formidable conventional military capabilities and the U.S. extended nuclear deterrent, which includes U.S. submarine-launched and intercontinental-range ballistic missiles as well as dual-capable fighter aircraft and strategic bombers that could be forward deployed in the region when needed.

If North Korea’s nuclear threat continues to grow, the answer is not for the United States to support a South Korean nuclear weapons program. It is to continue strengthening the U.S. extended nuclear deterrent.

To what extent can Washington bolster extended deterrence in response to allies’ concerns? 

President Biden and South Korean President Yoon have pledged to identify ways of reinforcing extended deterrence. The United States has agreed to increase the frequency and intensity of its rotational deployments to the region of U.S. strategic assets, to conduct high-profile demonstrations of U.S. commitment and resolve such as the participation of U.S. strategic bombers in joint air exercises, and to reactivate a high-level bilateral consultative group to address extended deterrence.

The South Koreans appreciate these steps but would like to see more, in terms of the forward presence of U.S. strategic assets and especially the role South Korea can play in formulating and implementing extended deterrence policies and in influencing crisis decision-making related to the possible use of nuclear weapons. The South Koreans will not get everything they want, but the U.S. government should be more flexible in giving its close ally a greater voice in matters affecting their vital interests.

How would a decision by South Korea to pursue its own nuclear weapons impact the ROK-U.S. alliance? And how would such a decision impact other U.S. alliances in the region, particularly with Japan?

South Korea’s acquisition of nuclear weapons would not necessarily mean the end of the U.S.-Republic of Korea mutual defense treaty. But the nature of the alliance would fundamentally change. The U.S. nuclear umbrella – the commitment to defend South Korea with nuclear weapons if necessary – would either be gone or significantly qualified. The United States presumably could still station military personnel in South Korea, but U.S. support for those deployments could erode. Why, Americans might ask, should the United States bear the costs and risks of keeping troops in the South when Seoul claims to be able to defend itself and no longer has faith in U.S. commitments?

A South Korean decision to acquire nuclear weapons could affect other U.S. alliances in the region. Many experts assume, for example, that if South Korea became a nuclear-armed state, Japan would follow suit, which would fundamentally affect the nature of the U.S.-Japan alliance.