Sen. Henry M. (Scoop) Jackson, 71, who personified strength in national defense, wariness in dealing with the Soviet Union, and liberal and pragmatic approaches to domestic problems, died Thursday at Providence Hospital in Everett, Wash., after a heart attack.

Sen. Jackson, a Democrat, had served in Congress since 1941, when he was elected to the House of Representatives. He moved to the Senate in 1953. The length of his service was matched by his influence. Until the Republicans took control of the Senate in 1981, he was chairman of the Energy and Natural Resources Committee, formerly the Interior Committee. He was a former chairman of the Government Operations Committee and its Permanent Subcommittee on Investigations. At the time of his death, he was the ranking Democrat on the Armed Services Committee and a member of the Select Committee on Intelligence.

But a list of his principal committee assignments hardly conveys the extent of his influence. Through his mastery of the ways of the Senate and the issues that concerned him, he became one of the most powerful and respected personages on Capitol Hill, an acknowledged authority on defense, energy, the environment and related issues.

In informal polls in the early 1970s, his colleagues picked him as the senator best qualified to be president and Senate aides chose him as the "most effective" senator. But he was unable to translate the high regard of his peers to the national electorate. In 1972 and 1976, he was roundly defeated in efforts to win the Democratic presidential nomination.

Throughout his career, he represented constituencies long associated with his party: organized labor, believers in a strong foreign policy and a defense industry to support it, minority groups, supporters of Israel, and the America of Rotary clubs and Masonic lodges. He maintained his vision of the country and its place in the world long after many politicians began to serve single-issue groups and leadership in many areas had passed from Congress to the executive branch.

His vision of America's interests led him to give unstinting support to the war in Vietnam, which he regarded as no less than a struggle between this country and the Soviet Union and its surrogates. He thus separated himself from many who were his allies on other issues.

The passions of Vietnam are illustrated by the campaign of Carl Maxey to take the Democratic senatorial nomination from Sen. Jackson in 1970. Maxey supporters carried signs referring to him as "Pentagon Pimp" and Maxey said: "Every time I see Jackson in that television commercial, walking in the woods with his child, I see the trees and I'm reminded of the coffins they are sending our children home in from Vietnam."

"I'm not going to beat Maxey, I'm going to bury him," the senator said. He received 497,309 votes to 79,201 for his opponent.

National security was the area on which Sen. Jackson left his strongest imprint. He once said that he regarded the Soviet Union "as an opportunistic burglar who walks down the corridors trying all the door handles to see which door is open." It was a conviction from which he never wavered and it shaped his world view. He had a high security clearance. This gave him access to intelligence reports, which he used to good effect.

In the early 1950s, he became a champion of Adm. Hyman Rickover, the "father of the nuclear Navy." On three occasions when the White House tried to retire the old sailor, Sen. Jackson forced presidents to promote him instead. For the Air Force, he favored more bombers, many of them made by the Boeing Co., the largest employer in Washington state.

In the same vein, he was skeptical of arms limitations agreements. In the early 1970s, he opposed the SALT I treaty until a clause was added that would give the United States parity with the Soviet Union on the number of rockets as well as the number of warheads. Later, he played a major role in the battle against SALT II. In 1974, he forced passage of the "Jackson amendment," which denied most favored nation treatment for the Soviets and other nations that do not permit the free emigration of Jews to Israel.

As chairman of the Interior Committee and then the Energy Committee, he directed Senate action on the environment and the oil crisis. In the late 1960s, he wrote the National Environmental Protection Act. He also wrote the Indian Education Act and the Alaska Native Claims Act. He was largely responsible for creation of the North Cascades and Redwood national parks and was the first politician to receive the John Muir Award from the Sierra Club.

He was a strong supporter of atomic energy and greater domestic exploration for oil. He was a member of the old Joint Committee on Atomic Energy for 30 years. He used the Permanent Investigations Subcommittee to investigate the profits of oil companies after the Arab oil embargo in 1973.

Henry Martin Jackson was born May 31, 1912, in Everett, Wash. His parents were Norwegian immigrants. He got his nickname, "Scoop," as a newsboy who delivered 74,880 copies of the Everett Daily Herald without a customer complaint.

He took a law degree at the University of Washington in 1935. He first got into politics in 1936 when he and a friend, John Salter, formed a bogus committee to support President Franklin D. Roosevelt. The regular Democratic organization became concerned and Jackson wound up as its president.

Two years later, he was elected prosecutor of Snohomish County and set about driving all liquor and pinball machines out of the county. For this he was called "Soda Pop" Jackson. In 1940, he was elected to the House. Except for a stint in the Army in World War II, he remained there until he went to the Senate. In the Senate, he was sometimes called "the senator from Boeing."

In the House, he was one of the first to vote against funding the red-baiting Committee on Un-American Activities. In the Senate, he first gained recognition for his skillful cross-examination on television of Sen. Joseph R. McCarthy (R-Wis.), the leader of witch hunts that claimed many innocent victims in the name of protecting the country.

In 1960, Sen. Jackson was mentioned as a possible vice presidential candidate on John F. Kennedy's ticket. Instead, he was named chairman of the Democratic National Committee. Following the election of Richard M. Nixon in 1968, he was said to have been offered two cabinet posts: State or Defense. He chose to remain in the Senate.

Sen. Jackson was stricken at his home in Everett. He had returned there Sunday from a trip to China. Shortly before he died, he held a news conference in which he said that the shooting down of a Korean Air Lines Boeing 747 with 269 persons aboard by Soviet aircraft was an "act of barbarism."

Survivors include his wife of 22 years, the former Helen Hardin, and two children, Marie and Peter.