The recent crisis on the Korean Peninsula has once again brought to the fore China’s support for North Korea, which many deem vital for Pyongyang’s survival. In explaining this support analysts typically cite two factors: Beijing’s fear that the North Korean regime’s collapse will bring untold numbers of refugees across the border into China, and Beijing’s fear of a unified, democratic, and pro-American Korea under Seoul’s leadership with a large U.S. troop presence stationed on the Sino-Korean border.
These factors probably accurately reflect Beijing’s strategic calculus. However, although possible, it’s not at all clear that a unified Korea under Seoul’s tutelage would in fact be as pro-American as Western and (presumably) Chinese policymakers assume. A number of factors could undermine this assumption.
The first one being the process that unification takes. Even assuming the North Korean regime collapses and is quickly unified under Seoul’s leadership, there are a number of different ways this can unfold. One of the most plausible is that Chinese troops would rush across the Yalu River at the same time that ROK troops came across the DMZ in the south. In the process China would come to occupy a sizeable chunk of North Korea, which would also likely contain some of Pyongyang’s nuclear and other WMD programs. Beijing would therefore have powerful leverage in bargaining the terms of its withdrawal from Korea. This would almost certainly be used to extract concessions from Seoul and Washington on the U.S. presence north of the DMZ.
Even if Chinese troops did not play a role in the immediate aftermath of the North Korean regime’s collapse, Beijing would still hold important cards to extract concessions from the U.S. and South Korea. The most important of these would be to help develop the former North Korean state following unification. It’s difficult to understate the immensity of this challenge. Although German unification was difficult, the income disparity between the two Germanys at the time of unification was estimated at 3:1 or 2:1. Comparable figures for North and South Korea today are anywhere between 1:15 and 1:40 and are almost certain to continue growing.
Upon becoming fully aware of their plight relative to their brethren in the South, North Koreans are presumably going to be eager to see their economic livelihoods improve. Seoul alone is simply incapable of bringing to bear enough resources to fulfill these ambitions. China would be best able to help develop the former state of North Korea, given its immense amount of capital, proximity, and current economic enterprises inside the country. Although Beijing would have a strong economic interest in participating in this development, threats to withhold aid, investment, and expertise would likely force South Korea to make concessions on America’s role in a unified Korea.
Finally, even if China did not overtly pressure leaders in Seoul, it’s not clear South Korea itself would support a huge, sustained U.S. presence in a unified Korea. Since its formation, the form the ROK-U.S. alliance has taken has been the unique byproduct of the threat from North Korea. During much of the Cold War Pyongyang’s conventional capabilities were menacing enough to keep leaders in South Korea interested in a large U.S. troop contingency. As Seoul’s economic miracle has led it to surpass the North in terms of conventional military technology and capabilities, Pyongyang has developed WMDs in general, and a nascent nuclear capability in particular, to enhance the threat it can pose to its southern neighbor.
Absent this threat from North Korea there would be little reason, from Seoul’s perspective, to continue to welcome a large amount of U.S. troops on its borders, particularly after the messy business of unification is completed. China’s growing military capabilities might be one rationale, especially given South Korea's disputed borders with China. At the same time, even now when Beijing supports the North, South Korea has shown a strong reluctance to play any part in an American-led regional security architecture, which most see as aimed at China. Furthermore, even with the common threat of North Korea uniting them, Seoul has continued to keep Japan at arm’s length. Absent the threat from North Korea, this reluctance would almost certainly grow.
Domestic politics in a unified Korea would also reinforce this. Already the Left in South Korea— which is traditionally more skeptical about the alliance with the U.S. — has come to power at various times. Without the threat of the North gone it could very well see it’s positioned strengthened relative to the conservative Right. Furthermore, regardless of political affiliation, leaders in a unified Korea are almost certainly going to need to harness the demonstrated power of nationalism to more tightly unify the formerly separate halves of Korea. Any leader relying primary on the ideology of Korean nationalism for their political survival is going to have a difficult time acquiescing to a large U.S. military presence on the Peninsula.
For all these reasons, then, it’s quite possible that China may gain strategically from a unified Korea relative to the U.S., or at least not be adversely affected by it. Although policymakers are right to focus on the immense difficulties that will likely immediately follow the collapse of the North Korean regime, they should not completely ignore the fact that such an event has the power to reorder the balance of power in Northeast Asia nearly overnight.