Richard A. Ericson Jr., 82, a former ambassador and career Foreign Service officer whose decision to disregard directions from Washington helped prevent a dangerous breach in relations between Japan and South Korea in the 1970s, died of a heart attack Dec. 1 at his home in Rockville.

Mr. Ericson was deputy chief of mission in Seoul on Aug. 15, 1974, when an ethnic Korean who lived in Japan opened fire at South Korean President Park Chung Hee at South Korea's National Theater. The assassin, who used a pistol stolen from a Japanese police officer, missed the president but killed his wife.

Tensions between the countries immediately escalated. The Japanese Embassy was besieged by Korean rioters, several of whom cut off their fingers to show their animosity, and then smeared the embassy wall with blood. The Japanese protested their innocence but refused to accept any responsibility for allowing the existence of a pro-North Korean group thought to be behind the attack. Preparations were underway to nationalize Japanese assets in South Korea if the crisis wasn't settled, according to "The Two Koreas" (1997), by The Washington Post's former diplomatic correspondent Don Oberdorfer, who witnessed the shooting.

Washington, preoccupied with the resignation of President Richard M. Nixon, ordered diplomats to stay out of the dispute.

"Disregarding instructions, Ericson . . . placed his career on the line and worked out a face-saving accommodation," Oberdorfer wrote. "In secret meetings with Japanese Embassy officials and South Korean prime minister Kim Jong-pil, Ericson arranged a carefully phrased Japanese letter of regret, pledges of a limited crackdown on 'criminal acts' of North Korean elements in Japan, and a peacemaking visit to Seoul by a respected Japanese elder statesman."

The Japanese foreign minister and South Korean government lavishly thanked Mr. Ericson for his role, said Donald P. Gregg, former ambassador to Seoul.

"In my more than 50 years of exposure to events in Asia, Dick Ericson's handling of that crisis stands out in my mind as one of the very best examples of successful diplomacy under pressure that I have ever witnessed," Gregg said.

Mr. Ericson, whom Oberdorfer described as "not a typical suave, striped-pants diplomatic type," had much experience in South Korea and Japan before that incident. Unlike many foreign service officers posted in three-year increments to countries that share little in common, Mr. Ericson carved out a specialty in South Korea and Japan early in his career and largely was able to stick to it.

Born in Honolulu, he served in the Army during World War II, with tours of duty in Korea and postwar Japan. He entered the Foreign Service in 1947 and was assigned to Yokohama, Japan. He learned Japanese at Harvard University, then returned to the embassy in Tokyo in 1953.

Back in Washington a few years later, he received a degree from Georgetown University's School of Foreign Service and worked in various State Department assignments.

Mr. Ericson worked at the U.S. Embassy in London, coordinating U.S. and British interests in the Far East, South Asia and Latin America. From 1965 to 1968, he was political counselor at the embassy in Seoul. He then spent two years at the embassy in Tokyo. After a stint in Washington as director for Japanese affairs at the State Department, he became deputy chief of mission in Seoul at the end of 1973. He was in charge of the embassy in August 1974 after Philip C. Habib left to become assistant secretary of state.

He returned to Washington in 1976 as deputy director of political and military affairs at the State Department. In 1978, President Jimmy Carter named him ambassador to Iceland.

Mr. Ericson retired from the Foreign Service in 1981 and became executive of the Japan-U.S. Friendship Commission in Washington. He retired in 1985.

Mr. Ericson delighted in a description of himself as a "fat, cigar-chomping diplomat, whose Tammany Hall manner belied a keen and incisive mind," his family said. Friends recalled a man with a good sense of humor and gruff exterior who held colleagues to high standards. He loved betting on horse races and reading poetry to his children. His wife, Elizabeth Wade Ericson, who died in 1992, helped establish the program that allowed the adoption of Korean orphans by U.S. citizens.

Survivors include five children, Richard A. Ericson III of Hopkinton, R.I., Martha E. Ericson of Cleveland, William W. Ericson of San Francisco, Kristin E. Secan of Brookeville and Charlotte E. Taylor of Bethesda; and eight grandchildren.

Ericson defused tensions after an assassination attempt in 1974.