William Gleysteen, 76, a career Foreign Service officer who was ambassador to South Korea from 1978 to 1981, a tumultuous period marked by the assassination of President Park Chung Hee, died Dec. 6 at the Washington Hospice. He had leukemia.

He spent three decades as a State Department specialist on Southeast Asia before President Jimmy Carter appointed him ambassador to South Korea.

His tenure coincided with unrest in South Korea following the assassination of Park in a 1979 coup, the imposition of martial law and a violent military crackdown on anti-government demonstrations.

Mr. Gleysteen wrote about these times and the U.S. response in his book "Massive Entanglement, Marginal Influence: Carter and Korea in Crisis," which won the American Academy of Diplomacy book award in 2000.

Upon his retirement from the Foreign Service in 1981, Mr. Gleysteen became director of the Asia Society's Washington Center. In 1983, he moved to New York, where he was director of studies at the Council on Foreign Relations and president of the Japan Society.

Mr. Gleysteen, who moved to Bethesda in 1995, was born in what was then called Peking and raised in a family of Presbyterian missionary-educators who lived and worked in China before and during World War II. In 1943, Mr. Gleysteen was interned by the Japanese along with his parents and younger brother.

He went on to serve in the Navy at the end of the war. He graduated from Yale University, where he also received a master's degree in international relations.

Fluent in Mandarin, he began receiving assignments in Asian affairs when he entered the Foreign Service in 1951. He was director of the Office of Intelligence and Research for East Asian and Pacific Affairs from 1969 to 1971 and deputy chief of mission in Taipei from 1971 to 1974.

From 1974 to 1976, and again in 1977 and 1978, Mr. Gleysteen was deputy assistant secretary of state for East Asian and Pacific affairs. He was also detailed to the National Security Council as senior staff officer for East Asia and the Pacific.

During these years in Washington, he served as senior adviser to two successive secretaries of state in the normalization of U.S. relations with China, a goal he sought to promote throughout his career.

His marriage to Zoe Gleysteen ended in divorce.

Survivors include his wife, Marilyn Wong Gleysteen of Bethesda; three children from his first marriage, Thea Clarke of Bethesda, Guy Gleysteen of Fairfield, Conn., and Michael Gleysteen of Ashburn; a daughter from his second marriage, Anna Wong Gleysteen of Bethesda; a sister; and seven grandchildren.