South Korea’s Nuclear Debate and the Credibility of U.S. Extended Deterrence

North Korea’s third nuclear test last month unleashed an active South Korean debate on nuclear weapons acquisition along with calls for the reintroduction of U.S. tactical nuclear weapons to deter and strengthen the U.S. and ROK position in nuclear negotiations. (The debate was nicely summarized here by Toby Dalton and Yoon Ho-jin). South Korea has also displayed its determination to counter any perceived North Korean advantage that might allow it to use nuclear blackmail against South Korea.  As the decibel level of North Korea’s threats has reached unprecedented levels, South Korea has also shown a grim determination to match North Korea’s threats with its own clear and specific signals of resolve.

A sustained high-level U.S. response to North Korea’s nuclear threats has also been in overdrive in recent weeks as it has attempted to send a complex set of messages to the region.  First, President Obama called President Lee following North Korea’s nuclear test to provide explicit assurance of its extended deterrence commitment to South Korea’s security under the U.S. nuclear umbrella. Second, National Security Advisor Tom Donilon insisted that North Korea “change course” and engage in “authentic negotiations” while delivering a stark warning that North Korea would be held responsible for nuclear terrorism resulting from its proliferation.  Third, Defense Secretary Hagel announced a $1 billion commitment to further development of missile defense despite the fiscal constraints imposed by the sequester.  Fourth, Deputy Secretary of Defense Ashton Carter visited Seoul during U.S.-ROK annual military exercises and noted B-52 strategic bomber participation in the exercises. News reports also highlighted  that the U.S. nuclear attack submarine USS Cheyenne carried out anti-submarine drills as part of the same exercises. Fifth, Treasury Undersecretary David Cohen arrived in Seoul on the heels of Ash Carter’s visit to discuss financial sanctions implementation before going on to Beijing. And this week, top U.S. envoy for East Asian and Pacific affairs Joseph Yun arrived in Seoul and is also expected to discuss North Korea’s nuclear and missile programs.

Through all of these activities, the United States has sought to simultaneously signal deterrence of North Korea and provide positive assurances to South Korea.  At the same time, the Obama administration has attempted to show China that Beijing’s policy of enabling North Korea’s provocative behavior carries tangible costs to regional stability in an attempt to win enhanced cooperation from China to deter North Korea from undertaking additional provocations.   The task of signaling all these messages  to respective target countries is critical to sustaining the credibility of U.S. extended deterrence commitments and to sustaining deterrence of North Korea, but there are also clearly some potential contradictory elements to the messaging that require careful management.  The most sensitive potential contradiction involves China’s tendency to think of the peninsula as part of a Sino-U.S. competition for influence and its belief that deterrence of North Korea is a convenient proxy for efforts to gain strategic advantage against China, especially as regards to missile defense. 

As part of an excellent volume edited by Jeffrey W. Knopf examining the role of security assurances in nuclear nonproliferation, I wrote a case study on the history of U.S. efforts to provide positive assurances to South Korea through a strong U.S.-South Korea  alliance. The takeaway from my chapter is that the Obama administration will have to constantly continue its efforts to provide assurance to South Korea regarding the credibility of U.S. defense commitments.  But in light of North Korea’s nuclear progress, U.S. assurances will likely be insufficient to assuage South Korean doubts about whether the United States will be willing to risk an attack on itself to protect its ally or “trade Los Angeles for Seoul.”  Whether the U.S. threshold for action meets South Korean expectations will emerge as a constant and unresolvable source of tension in the relationship.  The only way to resolve this newly-emerging tension will be for the United States and South Korea, in cooperation with China, to somehow find the right combination of measures to bring North Korea back to a path of negotiations accompanied by concrete actions in the direction of denuclearization.