Even as they recently celebrated the 30th anniversary of bilateral ties, South Korea and China couldn’t avoid clashing over one of the major points of friction in their relationship.

Following a meeting between their top diplomats last month, China’s foreign ministry reiterated its support for the so-called three nos agreement, under which the previous Moon administration reportedly promised that Seoul would not install additional THAAD missile interceptors, not join a U.S.-led missile defense network and not enter into a trilateral alliance with Washington and Tokyo.

The Yoon administration responded by stating that the deal is not a formal agreement and that the issue of whether it deploys more THAAD batteries is not up for negotiation.

The airing of differences did not exactly come as a surprise, as South Korean President Yoon Suk-yeol has been quite vocal about THAAD and the three nos deal since the campaign trail. But it’s all the more notable in light of the fact that, at least so far, he has not taken any steps that would constitute a violation of the deal itself.

What this suggests is that Yoon’s opposition to the three nos remains largely rhetorical. But words matter, and Seoul’s stance is still likely to impact its relations with Beijing. 

The key will be whether Yoon can stick to its message on the three nos without causing a deterioration in its ties with China. While Seoul has options, they each have associated risks, and it will have to thread the need to maintain good ties with Beijing even as it hews closer to Washington.

WORDS VS. ACTIONS

Both the Moon and Yoon administrations have argued that the three nos amount to nothing more than South Korea deciding not to do something, and China announcing it. Nevertheless, conservatives, including Yoon, fear that Moon painted South Korea into a corner through his public announcement.

Yoon was particularly outspoken against the three nos during his campaign, once posting the short message “additional THAAD deployment” on Facebook without elaborating. He has also sought to reinforce trilateral security cooperation with the U.S. and Japan.

In addition, the ROK president has adopted the so-called Three-Axis defense system, which includes deploying a South Korean missile defense system and more THAAD interceptors to cover the Seoul metropolitan area. 

Even so, nothing that Yoon has done so far actually violates the three nos as China appears to understand them. While he reinforced the installation of a THAAD battery already agreed upon, he has not taken any steps to deploy additional interceptors, including near the capital as he previously announced.

There are also no signs of South Korea joining a U.S.-led missile defense network either. Yoon’s plans for a Three-Axis system rely on ROK missile defenses, which does not violate the three nos. And in any case, these plans were first formulated under Moon, albeit under a different name.

A trilateral alliance is not on the horizon either. Yoon has agreed to resume joint military exercises with Japan and the US, but this is merely a return to pre-2017 policy. There have been trilateral discussions about working together in the Indo-Pacific generally, but talks have only revolved around trilateral cooperation, not an alliance.

These moves may together be part of a deliberate strategy to allow Yoon to look tough on China while maintaining economic ties. It could also be that he intended to implement policies that run counter to the three nos but became warier of the potential costs once in office.

The U.S. tests a THAAD missile interceptor on Aug. 30, 2019 | Image: U.S. Department of Defense Missile Defense Agency

PUBLIC VS. PRIVATE

The big question then is whether it actually matters that Yoon has altered Seoul’s public messaging on the three nos. And in all likelihood, the answer is yes.

States don’t just respond to material reality, but also how they perceive others’ intentions. Generally, reassuring messages can de-escalate tensions, whereas ominous threats aggravate them, and the effect of ambiguous signals is situation-dependent and, well, ambiguous. 

Countries face a dilemma when sending a reassuring signal to one state means alarming another. In this vein, taking a public stance for or against the three nos, even while keeping actual policy the same, brings different advantages. 

By publicly opposing the Moon-era agreement, Yoon can appeal to his conservative base and the U.S. But he could still face a backlash from supporters if he doesn’t actually pursue a change in policy that would violate the deal.

On the other hand, Moon was able to improve China-South Korea relations by agreeing to stick to the three nos, even if only behind closed doors. This included securing the lifting of retaliatory measures that Beijing implemented in response to the initial decision to deploy THAAD in South Korea.

Moon’s approach is likely off the table for Yoon given how much emphasis he has put on improving ties with the U.S. and in light of his low approval ratings, which make him more reliant on his conservative base.

But one option could allow Yoon to avoid the dilemma entirely: He could publicly oppose the three nos while privately reassuring China that it will stick to them. Beijing would be able to breathe a sigh of relief, while Yoon would not have to lose face and go back on his past promises.

The risk of this approach is that China could publicly reveal that Yoon made such reassurances behind closed doors, not unlike it did when the Moon administration reportedly said it would stick to the three nos. Yoon would further lose the trust of his supporters as a result, as well as of the U.S.

While Yoon could ask China to keep any promises about the three nos secret, it would be difficult to do this without revealing his cards. It would also be difficult for Yoon to keep information about Seoul offering reassurances to Beijing from leaking from within his own administration.

Publicly opposing the three nos while privately offering China reassurances thus seems like a suboptimal option for South Korea as well.

A BETTER APPROACH?

If Seoul does make some promise to Beijing behind closed doors, a better option would be to do so in a way that is ambiguous enough to give the Yoon administration plausible deniability, while still getting the message across.

A tell-tale sign that Yoon is pursuing such a strategy would be China softening its rhetoric on the three nos, which could occur if Beijing feels confident Seoul won’t violate them and thus sees less reason to reiterate its understanding of the agreement.

However, all of this assumes that security concerns are actually the cause of China’s focus on THAAD and the three nos, rather than serving as a pretext for other motives. For instance, some have accused China of making use of the situation to assert power over its neighboring countries or to bully South Korea. 

More likely is that these issues tie into China’s worry that South Korea will close ranks with the U.S. and balance against it. 

South Korea has an important question before it. Is it willing to risk Beijing’s wrath by openly balancing against it? If the past is any indication, the answer is no.

Edited by Bryan Betts