South Korea continued to depend on United States military assistance. In spite of initial United States hesitation about supporting Park in 1961, the two countries maintained close economic, military, and diplomatic ties. South Korea dispatched combat troops to the Republic of Vietnam (South Vietnam) in 1965 to augment United States forces there, and President Lyndon B. Johnson paid a personal visit to Seoul in October 1966 to show his appreciation.

Friction began to develop in the Washington-Seoul relationship after the United States withdrew one of its two divisions from South Korea in 1971 and intensified after Park instituted rigorous authoritarian measures under his 1972 constitution. This tension led to an accelerated effort by the Park government to gain support in the United States Congress. The methods used by Seoul's lobbyists ultimately resulted in the embarrassing "Koreagate" affair of 1977, involving former Ambassador Kim Dong-jo and rice dealer Park Tong Sun. Investigations by the Ethics Committee and by the Subcommittee on International Organizations of the Committee on International Relations of the United States House of Representatives received much press coverage and weakened United States support for South Korea.

During his presidential election campaign in 1976, Jimmy Carter pledged, if elected, to withdraw all combat troops from South Korea. His victory aggravated United States-South Korean relations considerably (see Relations with The United States , ch. 4). In March 1977, the United States decided to withdraw its ground combat forces over a four-to-five year period. Some 3,600 troops subsequently were withdrawn, but further reductions were suspended in 1979. In the meantime, President Carter and the Congress continued to press for the improvement of the human rights climate in South Korea. Relations between the two countries were at a low point in 1979, just before Park's assassination. In early 1981, President Ronald Reagan's administration announced that further withdrawals were not being considered.

Data as of June 1990