The U.S. military has contributed to the maintenance of peace and security in the Republic of Korea (ROK) for more than 67 years through three military commands: the United Nations Command, the United States Forces Korea and the Combined Forces Command. Each of these commands, at some point in their history, encountered significant developments in the strategic environment that necessitated adaptation of their mission or scope, a challenge to which each command rose in turn. The unwavering commitment of the U.S. military in Korea during this long period is a testament to the flexibility of these institutions, which have shown their ability to respond to the complex and changing threats in Northeast Asia. The conditions behind each command’s establishment help elucidate how the Republic of Korea came to be the only stable, democratic nation with its wartime forces under the operational control of a U.S. commander, to serve as the home of the only U.S. binational combined force and to be the location of the United Nations Command led by the U.S.

Kathryn Botto
Kathryn Botto was a senior 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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U.N. Command

The U.S. military presence in Korea began in earnest at the end of World War II in what was intended to be a minor and temporary measure to stabilize South Korea and counter potential Soviet expansion. Although originally proposed as a five-year trusteeship, it manifested as the U.S. Army Military Government in Korea. That military government ended in August 1948 with the election of ROK President Syngman Rhee and transitioned to a role as a military advisory group. After Rhee’s election, the U.S. began withdrawing its troops from the ROK. North Korea, meanwhile, started planning an invasion of the South, which it carried out on June 25, 1950.

After the outbreak of the Korean War, U.S. interests in Asia included countering Chinese, North Korean and Soviet expansion in the region. U.S. President Harry S. Truman was clear, both in private and public pronouncements, that his primary concern regarding Korea was the question of Soviet involvement in the conflict. In the early days of the war, the administration believed the North Korean invasion of South Korea might be part of a regional communist offensive by the People’s Republic of China (PRC) and the Union of Soviet Socialist Republics (USSR). Their first action was to send the U.S. 7th Fleet to protect the Republic of China (now Taiwan) to ensure it would not be invaded as well, according to U.S. Department of the Army records. A number of concurrent developments elevated Truman’s concerns regarding an increasingly broad and emboldened regional communist threat, including the Chinese Communist Party’s accession in the Chinese Civil War and the USSR’s first nuclear test in 1949. These factors contributed to Truman’s decision to extend aid to South Korea under the auspices of the U.N. to impede communist expansion abroad and shore up anti-communist credentials at home.

To accomplish this, the U.S. sought the endorsement of the U.N. Security Council (UNSC). The establishment of the U.N. Command (UNC) through UNSC Resolution 84 on July 7, 1950, granted the U.S. permission to act. The resolution stipulated that the U.S. designate the commander of a unified command, under the U.N. flag, to “assist the Republic of Korea in defending itself against armed attack and thus to restore international peace and security in the area.” Western nations perceived UNC actions as thwarting communist expansion potentially affecting the region and the world, and they were legitimized by broad international support. The unanimous endorsement of the resolution at the Security Council became possible due to USSR Premier Joseph Stalin’s decision not to send a representative to the meeting where the UNC mandate to participate in the Korean War was endorsed. Had the USSR blocked the resolution, it is unclear whether involvement in Korea would have had enough support in the U.S. Congress to proceed unilaterally. Instead, the UNSC decision set a precedent for U.S. military action abroad without a congressional declaration of war, which remains the standard today.

After a little more than a year of fighting, the U.S. (via UNC), PRC and North Korea supported the commencement of armistice talks to end the conflict as soon as possible. However, Rhee regarded the signing of an armistice agreement as negating any prospect for Korean unification under Seoul, and consequently, a threat to South Korean security. In his letters to U.S. President Dwight D. Eisenhower, he stated that signing an agreement that allowed Chinese communist forces to remain in the North represented “an acceptance of a death sentence without protest.”

After two years of negotiations and the Mutual Defense Treaty offer, Rhee still objected to the armistice and refused to sign. In the end, the armistice had five signatories: two American leaders from UNC, two from North Korea and one from the PRC.

Due to the failure to resolve long-term issues during armistice negotiations, the Korean Armistice Agreement relegated the settlement of “the Korean question” and the withdrawal of foreign forces from Korea to a political conference in Geneva. The uncompromising nature of Rhee and divergent goals in the North and South left few expectations the conference would succeed. Rhee lamented the conditions of the conference; he asked the U.S. ambassador how long he would need to wait before his allies realized the conference was merely a stalling tactic, that there would be no peaceful withdrawal of Chinese communist forces from Korea and no unification through a free U.N.-supervised election. The conference failed to produce an agreement to solve the Korea question. Instead, it resulted in the 38th parallel becoming a de facto border and the maintenance of an enduring armistice in lieu of a peace treaty. Because the armistice agreement was signed by the UNC commander and designated UNC as the administrator of the southern half of the Demilitarized Zone, UNC’s presence on the peninsula as the protector of peace and security in the area endured as well.

U.S. Forces in Korea

While the establishment of UNC was about regional strategic goals, U.S. Forces Korea’s establishment and sustained presence on the peninsula was initially a response to mistrust between the U.S. and ROK. As armistice negotiations were perpetuating UNC’s ongoing role on the Korean Peninsula, the machinations of Rhee and his goals for unification were impeding expeditious resolution of the Korean conflict. As the Korean War came to a close, the U.S. had to focus on supporting stability in South Korea while encouraging ROK restraint on North Korean issues, and thus offered the Mutual Defense Treaty as an assurance to the ROK. Although this move was a reaction to Rhee, the value of maintaining a strong anti-communist alliance in the Pacific warranted continued U.S. involvement in the ROK as well.

From the outset, U.S. interests concerning Korea and the treaty were regional, just as they had been with UNC. Indeed, the treaty’s language focused on strengthening the “fabric of peace in the Pacific area.” The ROK is mentioned largely in its role as party to the treaty, while the “Pacific area” is consistently referred to as the object of the treaty’s defense. U.S. government thinking behind the treaty centered on the potential for multilateral cooperation between bilateral treaty allies in Asia that Eisenhower and some senators referred to as a “NATO [North Atlantic Treaty Organization] of the Pacific,” according to U.S. Senate Committee on Foreign Relations testimony documents. Despite other bilateral treaties in the Pacific and the regional focus of the treaty, U.S. Army Gen. Matthew Ridgway and Secretary of State John Foster Dulles perceived the differences between Asian nations to be too great to form a NATO-like coalition.

Rhee’s vehement opposition to the armistice agreement was one of the primary reasons that Eisenhower conceded to the idea of a Mutual Defense Treaty. Rhee repeatedly threatened to take unilateral action against the North during negotiations. In 1953, he released about 25,000 Chinese and North Korean prisoners of war (POWs) who wished to remain in the democratic South, much to the surprise of China, North Korea and the United States. Attaining Rhee’s support had become so difficult that the U.S. had a contingency plan called Operation Plan Everready, as a possible means of overcoming Rhee’s objection to portions of the proposed armistice agreement. Some versions of the plan included provisions for subduing and replacing Rhee. The offer of a Mutual Defense Treaty was intended to dissuade Rhee from taking unilateral action against the North and to get him to agree to the armistice rather than resume the conflict. It did go a long way to assuage Rhee’s concerns, and he allowed negotiations to conclude. However, he still refused to sign the armistice agreement.

Combined Forces Command

Combined Forces Command (CFC) was the first command established as a direct response to North Korean capabilities rather than regional concerns. However, like the other commands, its scope and mission evolved to accommodate events. In fact, CFC was created in 1978 to facilitate the withdrawal of U.S. forces from the ROK, a major initiative for U.S. President Jimmy Carter that was later reversed by U.S. President Ronald Reagan in 1981. Reagan’s reversal came on the heels of revelations during the Carter administration that North Korean capabilities had developed much more than originally thought. Before the reversal, operational control (OPCON) of ROK forces was transferred from UNC to CFC and the terms of reference for the commander in chief, UNC, were changed in 1983 to reflect the existence of CFC as a “separate legal and military entity from UNC.”

CFC was first floated as an idea in the early 1970s, when the changing regional dynamics prompted consideration of the dissolution of UNC in the interest of detente with the PRC and a peace treaty with North Korea. Both the ROK and the U.S. supported the termination of UNC but for different reasons. For the U.S., dissolving UNC would help its efforts to normalize relations with the PRC. An internal NSC memorandum documented that the U.S. intended “to work primarily in parallel with the PRC both to backstop and to restrain our respective Korean allies as necessary” in negotiations. Additionally, U.S. President Richard Nixon’s doctrine’s goal of giving allies domestic control of their own defenses justified dissolving UNC, which still maintained OPCON of ROK forces at this point, some experts contend. CFC would have facilitated transfer of OPCON to the ROK under this initiative.

The ROK perceived U.S.-China rapprochement and the Nixon Doctrine as motivating factors for the dissolution of UNC in a different way. Park Chung-hee feared the ROK might become isolated as the U.S. improved relations with the PRC and that the U.S. might pursue diplomatic relations with North Korea as well, according to a history published by the Wilson Center. Park sought inter-Korean dialogue to secure security guarantees for the peninsula in the event of U.S. troop withdrawal. Thus, talk of UNC termination became a helpful piece of the negotiating package between the two Koreas. As it turns out, the U.S. did consider expanding relations with North Korea during this time, although it preferred to wait until after UNC termination, because doing so before might cause North Korea to be “encouraged toward intransigence” and make negotiations more difficult, according to a NSC memorandum.

These negotiations were not successful in terminating UNC, largely because of the inability of the two Koreas to agree on terms, not due to Sino-U.S. conflict. Both the U.S. and PRC expressed the desire to continue involvement maintaining the armistice. However, North and South Korea each submitted conflicting resolutions to the U.N. General Assembly on the UNC issue in 1975. It marked the first time a North Korean proposal on the Korean question was debated in the General Assembly, because North Korea had only recently begun to be involved in the U.N. after the dissolution of the U.N. Commission for Unification and Reconciliation of Korea, U.N. General Assembly records reveal. However, the North Korean resolution called for complete withdrawal of U.S. forces from the peninsula, while the ROK proposal called for dissolution of UNC but maintaining U.S. forces in the South, experts documented. In the end, the two resolutions could not be reconciled, UNC was not dissolved, and inter-Korean relations stagnated.

During the UNC termination negotiations, the U.S. considered various methods of maintaining OPCON of ROK forces. U.S. Secretary of State Henry Kissinger stated that the most “practical and, for the South Koreans, the most reassuring replacement for UNC” would be OPCON by a new U.S.-ROK combined command headed by the U.S. senior officer. The deadlock at the U.N. General Assembly over UNC’s fate in 1975 ended aspirations for the establishment of a combined command until it became the facilitating institution for Carter’s withdrawal policy.

Carter’s commitment to withdrawing forces from South Korea originated as a campaign promise motivated by reluctance to support long-term overseas stationing of ground forces, then President Park Chung-hee’s human rights record, as well as fear of a so-called tripwire, or automatic military involvement in hostilities. However, intelligence community estimates at the time cited mounting evidence that North Korea’s military strength was much greater than previously thought. The Carter administration did not heed the advice of the intelligence community and pushed ahead with the decision until the corroboration of intelligence estimates became so great that Carter was forced to modify his position. Carter announced that the withdrawal policy would be reconsidered in 1981, but he lost the re-election and the policy was promptly scrapped by Reagan. However, CFC remained in place.

Shared agility

Each of the three commands during their tenure have encountered developments in the security environment that have necessitated an adaptation of their mission. For UNC, this was the failure of the Geneva Conference, which led to UNC being a permanent fixture maintaining the armistice on the peninsula. Rhee’s demonstrated willingness to provoke the North, such as through the release of POWs, prompted a reconsideration of the U.S. approach to the region that included the establishment of U.S. Forces Korea. For CFC, the revelation of North Korea’s improved capabilities forced the U.S. to re-examine its commitment to the ROK. Rather than being overtaken by events, the three commands have proven their resilience and ability to evolve and address rising security challenges in Northeast Asia.

This article was originally published in Indo-Pacific Defense Forum.