South Korea Will Stay Out of a Taiwan Strait War

The increasingly discussed possibility that China may attempt to annex Taiwan by military force appears to have strengthened the resolve of the United States and Japan to help defend Taiwan. South Korea, however, is reacting differently. Yes, Seoul is a U.S. ally and a liberal democracy, and the majority of South Koreans strongly dislike China. But South Korea’s approach to China – and Taiwan – is complicated.

In no case would South Korea offer zero support to Taiwan in the event of war. The question is at what point along the spectrum of possible assistance Seoul would position itself. There is good reason to think South Korea would limit its support to actions near the low end of the spectrum – strong diplomatic statements, symbolic economic sanctions, and behind-the-lines re-supply of U.S. forces returning from battle – in the hopes of avoiding a direct confrontation with China.

An attempt by China to invade Taiwan would probably include missile strikes against bases in South Korea, especially the U.S. Air Force base in Osan. Beijing would presumably leave ROK Navy bases alone unless South Korean warships appeared to be moving to attack Chinese forces. Seoul’s desire to limit the damage in its relations with Beijing is strong enough that strikes on South Korean territory that killed only Americans would not necessarily bring South Korea into the war as a combatant against China.

The South Korea-Taiwan relationship illustrates how vital national interests often supersede “shared values” and historical friendships. The Republic of China (ROC) was the second country, after the United States, to recognize South Korea as a state in 1948. The ROC – by then sequestered in Taiwan – also made a contribution to the Korean War, sending Chinese-speaking soldiers to assist with intelligence assessment and processing of captured People’s Republic of China troops. Both Taiwan and South Korea were non-communist portions of divided nations, engendering a sense of kinship.

Despite all this, Seoul threw Taiwan under the bus in 1992. In May 1992, South Korean President Roh Tae-woo told a visiting official from Taiwan that he did not intend to sever Seoul’s diplomatic relations with Taipei. Three months later the South Korean government announced it was switching diplomatic relations from Taipei to Beijing, and that ROC staff had three days to vacate their embassy.

The election of Yoon Suk-yeol as president in 2022 heralded a possible change in South Korea’s orientation. A conservative who positioned himself during his presidential campaign as a China hawk, Yoon would seem to be relatively inclined toward supporting Taiwan. Even under Yoon’s leadership, however, South Korea’s policy still broadly seeks to maintain a constructive relationship with Beijing while simultaneously appearing to be a loyal ally of the United States.

Yoon has made several moves that suggest he, much like his predecessor Moon Jae-in, is being careful to not antagonize Beijing. Yoon initially said he would seek formal membership for South Korea in the Quad, which China vilifies, but he now seems content with informal membership and selective participation in non-security issues.

Likewise, Yoon initially rejected Moon’s “three noes” pledge to China regarding the Terminal High Altitude Area Defense (THAAD) system and said he would deploy additional missile batteries. But his nominee for defense minister later said that Yoon had decided additional deployments were not “realistic.”

On another issue of high sensitivity to Beijing, Yoon’s government says it has “no intention of participating in the U.S. missile defense system.”

In August 2022, apparently out of deference to Beijing, Yoon avoided meeting with then-U.S. House Speaker Nancy Pelosi when she stopped over in Seoul after her controversial visit to Taiwan.

Seoul perceives three compelling reasons to stay out of a Taiwan Strait war. First, South Korean prosperity relies heavily on robust economic relations with China. The China market accounted for 30 percent of South Korea’s total trade in 2022. South Korea’s high-tech sector is especially heavily China-exposed. Most of South Korea’s supply of rare earth elements comes from China, and China purchased 40 percent of South Korea’s semiconductor exports in 2021.

Second, Seoul believes that a Taiwan war will increase the North Korean threat to South Korea. The argument is that a U.S. decision to defend Taiwan from China’s military action would pull U.S. forces out of South Korea. This would tempt Pyongyang to launch an invasion, possibly as part of coordinated plan with Beijing to divide U.S. forces. Another version of the argument is that a distracted Washington would be more easily intimidated by North Korean missile and nuclear tests and therefore more likely to make unwise concessions in Pyongyang’s favor.

In such a situation, the argument goes, South Korea would need to double-down on its own defense, not expend resources to help Taiwan. Yoon told a CNN interviewer in September 2022 that in the event of a Taiwan Strait war, his “top priority” would not be assisting Taiwan, but rather guarding against an opportunistic North Korean attack.

South Korea is arguably capable of defending itself against North Korea even without U.S. forces. Moreover, the notion that a Taiwan Strait war would cause the United States to leave South Korea undefended is fallacious. Most U.S. military personnel in South Korea are U.S. Army soldiers, who would not play a significant role in a cross-strait war and would therefore be unlikely to leave the Peninsula. No U.S. Navy ships or aircraft are permanently based in South Korea. The U.S. assets now in South Korea that would be most useful in a Taiwan scenario are the aircraft of the 7th Air Force at Osan Air Base. The net impact of a cross-strait war is that U.S. Army presence in South Korea would be unchanged, and while some Korea-based U.S. airpower would be preoccupied, the overall quantity of U.S. aircraft on the Peninsula would likely increase as the United States surged additional forces into the region.

A third reason for staying out of a war against China is the South Korean government’s belief that a friendly Beijing can be a moderating influence on North Korea. Unfortunately, China’s usefulness to South Korea as a restraint on Pyongyang has always been overrated. North Korea continued to develop missiles and to conduct nuclear test explosions even when China seemed willing to apply countervailing pressure. More recently Beijing has relaxed its enforcement of economic sanctions while calling more forcefully for the United States and other countries to drop those sanctions.

Yet another reminder of how Beijing can be an enabler rather than a restrainer of North Korean misbehavior came with the resumption of a large South Korea-U.S. joint military exercise in mid-March, which was accompanied by another spate of North Korean missile tests. A Chinese Foreign Ministry spokesman’s comment said nothing about the North Korean missile launches, which violated a U.N. Security Council prohibition. Instead, he said China is “gravely concerned” about the military exercises and blamed tensions on the United States for “refus[ing] to respond to the denuclearization measures taken by” North Korea.

Allies of great powers often have two opposite fears. One is being abandoned by the great power and left alone to face a threatening adversary. The other is being dragged by the great power into an unwanted war. The possibility of a Taiwan Strait war raises both of these dangers for Seoul. If Americans perceived that an ally was unreasonably unhelpful in a time of need, the South Korea-U.S. alliance might be in jeopardy. By assisting its ally, however, South Korea would sacrifice its objective of maintaining a constructive relationship with China.

In its own way, South Korea would suffer in a cross-strait war – but not enough to offer Taiwan serious assistance.