PORTLAND, Ore. (AP) -- As a 23-year-old Navy officer in 1945, Mark Hatfield was among the first American servicemen to personally see the destruction wrought upon Hiroshima by an atomic bomb. It was an experience that helped shape Hatfield into an outspoken critic of war as he went on to become a two-term Republican Oregon governor, then the longest-serving U.S. senator in Oregon history.

Hatfield - one of the most influential politicians this state has seen - died in Portland Sunday night at age 89, said his longtime friend and former aide, Gerry Frank. The Oregonian reported he passed away at a care center. The cause of death was not immediately released. Hatfield had become increasingly frail over the years.

He was elected governor of Oregon in 1958 and re-elected in 1962 before winning his first U.S. Senate campaign in 1966. He served five terms in the Senate, from 1967 to 1997.

Hatfield is best known at the national level for his pacifist ways, which often put him at odds with fellow Republicans but endeared him to many Oregonians.

At the 1965 National Governors Conference in Los Angeles, he was denounced as a traitor for casting the lone "no" vote among 50 governors on a resolution supporting President Johnson's policy in Vietnam. In the early 1970s, he joined then-Democratic Sen. George McGovern of South Dakota to sponsor an amendment seeking to end the Vietnam War. A decade later, he helped launch a campaign for a nuclear weapons freeze.

Oregonians are remembering Hatfield for his considerable accomplishments and for an independent streak the moderate Republican showed during five decades in public office.

"Senator Hatfield played an enormous role in making Oregon what it is today," said U.S. Sen. Jeff Merkley, a Democrat. "He should also be remembered, in this age of bitter partisanship, for his bipartisan and gracious diplomacy."

Similar words were spoken by U.S. Sen. Ron Wyden, another Democrat: "He was a giant and the kind of senator America needs now more than ever. He was the person who brought the Senate together on issue after issue."

As chairman and later ranking Republican on the Senate Appropriations Committee, Hatfield steered millions of dollars to public works projects in his home state. They ranged from national scenic areas and hydropower dams to the state university system and the Marine Science Center that bears his name in Newport, Ore.

"No one has had a more profound impact on Oregon in the last half century than Mark Hatfield," said Gov. John Kitzhaber, a Democrat. "We've lost a true statesman whose legacy lives on in his countless contributions to Oregon's quality of life. Senator Hatfield's moral compass, independence and willingness to reach across the aisle are an inspiration to me and countless Oregonians."

Allen Alley, chairman of the Oregon Republican Party, called Hatfield "a quintessential Oregonian and a true national statesman. In his exemplary career as Republican U.S. Senator, Governor, Secretary of State and State Representative, he will be remembered for his courage and conscience in a life of public service for the people of Oregon and the country."

Hatfield once said that one of his major accomplishments was to usher through Congress a ban on U.S. nuclear weapons testing in 1987.

"Every president other than Eisenhower has been seduced by the military concept that that is our sole measurement of our national security and the more bombs we build, the more secure we are," Hatfield said a decade later.

"That's just not true. We are vulnerable in our national security today and we are vulnerable in many ways we are not addressing - the needs of education, the needs of housing, the needs of nutrition, the needs of health, the needs of infrastructure."

The devastation witnessed by Hatfield as a young naval officer at Hiroshima in 1945 helped shape his politics. When the war was officially over, Hatfield and his shipmates were instructed to take a boat and chronicle what was left of Hiroshima.

"There was a deathly silence," Hatfield said in a 1999 interview with The AP. "There was nothing happening in a big area that once had been a city. Now it was totally quiet except for the sound of our voices."

A devout Baptist, Hatfield frequently spoke out for the sick, the homeless and others in need of an advocate.

In a hushed congressional hearing room in 1990, he pleaded for increased money for Alzheimer's research while describing how the disease had reduced his father, a powerfully built former blacksmith, to a "vegetable."

He also criticized the death penalty and opposed abortion, though he never actively sought to place legal limits on abortion. He said his views on both issues were based on his belief in the sanctity of life.

Although Hatfield earned a reputation for integrity, his image was tarnished by a pair of ethics investigations in the 1980s and `90s.

In 1984, it was disclosed that Basil Tsakos, a Greek financier, paid $55,000 in real estate fees to Hatfield's wife while Hatfield was promoting Tsakos' trans-Africa pipeline proposal. Hatfield denied wrongdoing.

Then in 1992, Hatfield was reprimanded by the Senate Ethics Committee for failure to report thousands of dollars worth of gifts from James Holderman, former president of the University of South Carolina. Hatfield said the reporting failure was inadvertent.

Born in Dallas, Ore., Hatfield taught political science and was dean of students at Willamette University. He served in the Oregon House from 1951 to 1955, and then was in the Oregon Senate from 1955 to 1957. He was Oregon's secretary of state from 1957 until his inauguration as governor in early 1959.

Hatfield never lost an election, except in his college days when he was defeated in his bid to become student body president at Willamette University in Salem.

Among the buildings named in his honor were the Mark O. Hatfield Library at Willamette University in Salem, and the Mark O. Hatfield U.S. Courthouse in Portland.

He was author or co-author of several books, including "Against the Grain: Reflections of a Rebel Republican."

Hatfield and his wife, Antoinette, had four children.

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