Over the past year, the United States and South Korea have scaled down and suspended their combined military exercises to buoy diplomatic efforts to get North Korea to denuclearize. In response, North Korea has conducted several missile tests in the past month and rejected further peace talks with South Korea.

These exercises are an important part of a strong defense posture, not just a tool to gain leverage over North Korea. They allow South Korea and the United States to play through their responses to various military contingencies.

The current round of exercises, underway until August 20, are particularly vital. They test South Korea’s ability to assume operational control (or OPCON) of a combined U.S.–South Korean force during wartime. Notably, this is the first time Seoul has led such exercises in the history of the alliance.

How the Military Alliance Works Now

As things currently stand, South Korea has operational control of its military under armistice conditions, but the United States would take over in wartime. This arrangement is unique to the U.S.-South Korea alliance. It is reflected in the structure of the Combined Forces Command—the alliance’s war-fighting command—which is headed by a U.S. four-star general while a South Korean four-star general serves as deputy commander. Seoul is leading the current exercise to evaluate whether it is ready to take full operational control in wartime (or check the South Korean military’s initial operating capability). Initial operating capability is the first of three benchmarks to determine if operational control can be transferred to South Korea.

Kathryn Botto
Kathryn Botto is a research analyst in the Asia Program at the Carnegie Endowment for International Peace. Her research focuses on Asian security issues, with particular emphasis on the Korean Peninsula and U.S. defense policy towards East Asia.
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At a basic level, operational control refers to the “authority to perform functions of command over subordinate forces.” So if the armistice is violated and war breaks out, the U.S. combatant commander would be able to direct, organize, employ, assign command functions to, or suspend the duty of subordinate South Korean commanders and forces.

But this control has limits. The commander is subject to the authority of both the U.S. and Korean presidents (who are the National Command Authorities). This restricts his or her ability to make unilateral decisions for both the United States and South Korea. The military alliance also has solid mechanisms in place to encourage combined decisionmaking. When the United States turns over operational control to South Korea, those mechanisms will stay, but the South Korean commander in charge will have the power to make certain strategic decisions in war where he or she did not before.

How the United States Ended Up in Command

South Korea has not had wartime operational control of its forces since before the Korean War. On July 14, 1950, then South Korean president Syngman Rhee handed control of the fledgling South Korean military to General Douglas MacArthur, the commander of the United Nations Command (UNC). After the war, the Korean Armistice Agreement stipulated that South Korean forces would remain under the UNC commander’s operational control. This set-up was supposed to lessen concerns in the United States that “the United States forces can, against their will, be embroiled in a conflict initiated by [South Korea].”

The commander of UNC kept operational control until 1978, when the Combined Forces Command was created to ease U.S. president Jimmy Carter’s plan to withdraw U.S. troops from South Korea, a decision president Ronald Reagan later reversed. The U.S. commander of the Combined Forces Command had full operational control of South Korean forces until 1994, when Seoul took over operational control during armistice conditions, while the U.S. commander would only have operational control if war resumed. This arrangement continues to this day.

Why Operational Control Matters to South Koreans

Not many people in the United States have heard of operational control. But it is a major political issue in South Korea, especially for progressives. It was among Moon’s core campaign pledges, one he aims to accomplish by the end of his term in March 2022.

Operational control is largely a sovereignty issue. Because the current system started due to a perceived need to restrain Seoul, many in South Korea see it as infantilizing. The control of a country’s military is inherently supposed to rest with the sovereign nation’s authorities—in this case, South Korea.

In the public consciousness, U.S. operational control is also linked to a painful part of Korean history. In 1980, South Korean dictator Chun Doo Hwan used force against pro-democracy demonstrators in Gwangju, killing hundreds. At the time, the South Korean military was under the operational control of the United States. This made it seem as though Washington was complicit in the massacre, or at least could have done more to stop it.

Is Seoul Ready for Wartime Operational Control?

Operational control used to be tied to a continuously extended deadline. Moon’s predecessor, Park Geun-hye, agreed with the United States to base its transfer on three conditions. According to this rubric, Seoul should have: the “key military capabilities” to spearhead the two partner’s combined defense, the “essential capabilities” to respond to Pyongyang’s nuclear weapons program, and a “conducive” security environment for transfer.

These conditions improve South Korea’s defense posture and provide justification for Seoul acquiring more advanced capabilities. Seoul has made major progress toward meeting these conditions. However, they are in place because they were agreed upon as conditions between the two allies—not because they are inherently necessary to transfer operational control.

South Korea is an Anomaly

To understand why the conditions are unnecessary, one can look at other instances in which the United States has had operational control over another military. For example, the United States has previously had operational control of U.S.-led combined, multinational forces in places like Iraq and Afghanistan. But in these instances, the United States supplied the bulk of the forces under U.S.-led commands, while the majority of other nations’ forces remained under the sovereign’s operational control.

If war breaks out on the Korean Peninsula, however, South Korea would supply the overwhelming majority of the fighting force, which would then be placed under U.S. operational control. This is the case even though the South Korean military is a highly modernized, near-peer force. Other nations with similarly advanced forces, like Japan, have robust military cooperation with the United States without being under its operational control. Even less advanced militaries, like the Iraqi military, maintain operational control of their own forces while still cooperating closely with the United States.

What’s more, other instances of U.S. operational control of foreign militaries have been temporary—in South Korea, this structure has become more or less permanent.

South Korea is the only place where there exists a long-standing arrangement, in which a US-led command will assume operational control over the majority of a sovereign state’s forces in the event that that sovereign state is attacked. South Korea could lead the Combined Forces Command already, just as other nations lead their own fighting forces. Whether or not it will is more of a political question than a practical one. Transferring operational control will go a long way toward strengthening essential elements of a solid military alliance—trust and respect.