Late in 1962, President John F. Kennedy asked one of his closest congressional friends, the man he had hand-picked as majority leader of the US Senate, to assess the uncertain political situation in South Vietnam. As a former professor of far eastern history, Senator Mike Mansfield, who died on October 5th aged 98, knew the country and its leaders well.
In a confidential report to Kennedy, Mike Mansfield said he saw little point in the US continuing to support President Diem's tottering regime. Kennedy, publicly committed to such support, was furious.
Within a year both Diem and Kennedy had been assassinated, successive governments in Vietnam had grown ever more remote from reality, and President Lyndon Johnson had embarked on his disastrous military intervention. Had Mike Mansfield's advice been heeded, the US might have avoided one of the most traumatic episodes in its history.
It was, however, typical of the senator that, although he vigorously sustained his opposition to the war and to many more of Johnson's foreign policies, he lent his considerable clout to getting the president's domestic legislation onto the statute book. Without Mike Mansfield's low-key but persistent efforts, neither the Civil Rights Act, the Voting Rights Act, nor many of the other measures that transformed American life would have passed into law as effectively as they did.
The irony of Mike Mansfield's ascent to the majority leadership - a position he held under four presidents for an unparalleled 16 years - was that he never aspired to the job in the first place. Just four years after he was elected in 1952 as Montana's junior senator (joining a legislature where length of tenure governed virtually all advance), he was bulldozed by Johnson into becoming the Democratic whip.
Mike Mansfield's amiable character, unending courtesy, and capacity to fashion compromises on the most intractable issues soon established his reputation among senators on all sides. When Kennedy came to the White House in 1961, he had no doubt who should replace Johnson as leader of the Senate Democrats. It was, however, not as easy a ride as the president anticipated. Behind Mike Mansfield's gentle manner lay firmly held views which he expressed freely. Vietnam was only one of the issues on which he and Kennedy differed.
He was born in New York, to the wife of an Irish hotel porter. His mother died when he was three years old and he was sent to Montana, into the custody of an aunt and uncle who owned a grocery shop. From an early age they sent him out to deliver goods. He repeatedly ran away from home and eventually, with the US about to enter the first World War, dropped out of school, lied abut his age, and enlisted in the navy at 14.
He had completed several Atlantic crossings in the crew of a troopship before the authorities found him out and discharged him. He then joined the army and later transferred to the marines, with whom he was posted to the Philippines and China. His experiences there sparked a lifelong fascination with the Orient. After two years' service, he left the marines to shovel copper ore 2,000 feet underground in his adopted state.
Mike Mansfield's period in the mines introduced him to the raw politics of big business battling against big labour. It was not to his taste, and he realised that education was his best route out of this unpleasant morass.
He first enrolled at the Montana School of Mines and then, at the prompting of his future wife, school teacher Maureen Hayes, completed his secondary education by correspondence course. That led to a master's degree in history from the University of Montana, and to an appointment in 1933 as its professor of Far Eastern and Latin American history. By 1940, at the age of 37, he was becoming increasingly interested in politics, and stood unsuccessfully for the state's single seat in the House of Representatives. Two years later he tried again and won. When he arrived in Washington, the House Democrats immediately recognised his specialist knowledge and assigned him to the foreign affairs committee.
Mike Mansfield served four terms in the House, but his brand of moderate politics was generally out of tune with the times. As the rhetoric of the Cold War grew ever shriller, his decision to run for the US Senate in 1952 attracted some heavyweight opposition from Senator Joseph McCarthy.
However, McCarthy's red-baiting invective made little impact in Montana, and he won the seat in the face of a Republican landslide in the other western states. He retained it with ease for the next 24 years.
His assumption of the Senate majority leadership in 1961 came at one of the most stressful periods of American history. Kennedy's assassination in 1963 was followed by those of Martin Luther King and Robert Kennedy. The Supreme Court's abolition of segregation sparked widespread racial unrest across the southern states. The Vietnam War brought uproar to the universities, the Cold War created endless uncertainty, the Middle East repeatedly exploded. And finally, there were the revelations of the Watergate scandal.
In the 1950s, he came into a chamber encrusted with absurd traditions, controlled by pompous old men, many of whom had long outlived their purpose. He left it in 1977 having created a more civil climate. He dispersed power to the chairmen of the many specialist committees and encouraged younger members to take part in the legislative process.
When he left the Senate at the age of 74, President Jimmy Carter asked him to serve as US ambassador to Japan and President Ronald Reagan kept him in the post for a further eight years. On his return to the US he became a senior adviser to the investment bankers Goldman Sachs, where he continued to work almost until his death.
His wife Maureen, whom he married in 1932, died last year. They are survived by their daughter.
Michael Joseph Mansfield: born 1903; died, October 2001