Factbox: U.S. and South Korea's security arrangement, cost of troops

SEOUL (Reuters) - The 70-year security alliance between the United States and South Korea is under fresh focus as Washington seeks a sharply higher share of cost to be borne by Seoul for hosting U.S. troops as deterrence against North Korea.

The following are details of their security arrangement, military cost-sharing talks, and U.S. troops presence in South Korea.


At the end of the 1950-1953 Korean War, the United States and South Korea signed a treaty of mutual defense, where the two countries agreed to collective self-defense should either be threatened in the Pacific region. The deal provided the basis for U.S. armed forces’ stationing in South Korea.

In 1966, the two countries signed the Status of Forces Agreement (SOFA), which laid down the rules governing and protecting U.S. personnel stationed in South Korea.

The agreement’s Article V says the United States will bear all costs for U.S. troops’ maintenance, except those to be borne by South Korea, which included furnishing and compensating for “all facilities and areas and rights of way”.


To determine South Korea’s contribution to the cost U.S. troops as described in SOFA, the two countries have signed Special Measures Agreements, or SMAs, 10 times since 1991, usually to cover multiple years.

Under the last agreement, reached in February 2019 for one year, South Korea agreed to increase its contribution to just under 1.04 trillion won ($927 million), an increase of about $70.3 million from the previous deal.

Negotiations are ongoing over South Korea’s contribution for next year.

The United States has initially asked South Korea to pay $5 billion, a five-fold jump, a South Korean member of parliament said after his discussions with senior U.S. officials.

U.S. President Donald Trump has previously described U.S. troops’ presence and activities in and around South Korea as “$5 billion worth of protection”.


There are about 28,500 U.S. troops stationed in South Korea, according to South Korea’s Ministry of National Defense.

It is the third-largest presence of U.S. troops outside the continental United States after Japan and Germany, according to data from the U.S. Defense Manpower Data Center.

U.S. Forces Korea operates about 90 combat planes, 40 attack helicopters and about 60 Patriot missile launchers, according to South Korea’s Defense White Paper issued in December.

According to U.S. Forces Korea’s latest compiled weekly data, the Army had about 19,500 soldiers stationed in South Korea, the Air Force had about 7,800 airmen and women, the Navy had about 350 sailors, and the Marine Corps had about 120 Marines.

Major bases include U.S. Army Garrison Humphreys in Pyeongtaek, south of Seoul, U.S. Army Garrison Yongsan in central Seoul, and Camp Walker in Daegu, southeast of Seoul. The U.S. Air Force has two bases in Osan and Gunsan, south of Seoul.


In past cost-sharing agreements, South Korea only paid for three categories - personnel costs of South Korean workers hired by U.S. troops, military construction costs such as building facilities within U.S. bases, and military assistance expenses, such as for services and materials.

The United States is seeking an additional category of costs to be paid by South Korea in the ongoing negotiations, South Korea’s foreign minister has said, without elaborating.

According to South Korea’s Defense White Paper, out of about 932 billion won South Korea contributed in 2015, personnel costs were about 37%, construction costs were bout 45%, and the rest was for military assistance expenses.

Reporting by Joyce Lee; Editing by Jack Kim and Lincoln Feast.