Contemporary politicians who are struggling to determine when the time will be right to start talking about withdrawing troops from Iraq would do well to borrow a page from former U.S. Senator Gaylord Nelson, D-Wisconsin.

In the spring of 1964, when only about 16,500 U.S. troops were present in the country as “advisers,” and when no one had heard of the Gulf of Tonkin, Nelson was asked by a television reporter to discuss the U.S. presence in southeast Asia. Nelson responded by suggesting that President Lyndon Johnson should reconsider the decision to commit troops to the region, arguing that the time had come to “set some timetable for withdrawal from the situation.”

The Wisconsin senator completely rejected the notion that any good would result from an escalation in the U.S. role in the troubled country.

“I don’t think that additional men and materials and economic aid … is going to solve the problem in South Vietnam,” asserted Nelson, who repeated his counsel that the time was coming for “an orderly withdrawal.”

As the senator’s biographer, Bill Christofferson, noted, “Nelson knew almost from the start that the Vietnam War was a mistake.”

Even more significantly, Nelson had the courage to express that opinion when few others were willing to do so.

To be sure, Nelson, who died last week at age 89, will be most remembered as the originator of Earth Day. And his role in launching the contemporary environmental movement certainly merits recognition and praise. But it is important to recall that Nelson’s green activism was only a part of his broader progressive vision and commitment.

Raised in the Wisconsin progressive tradition of former U.S. Sen. Robert M. “Fighting Bob” La Follette, who courageously and correctly opposed Woodrow Wilson’s decision to march U.S. troops into World War I, Nelson emerged in the mid-1960s as an equally courageous and correct critic of Johnson’s misadventure in Vietnam.

After being assured by Sen. J. William Fulbright, the respected chair of the Senate Foreign Relations Committee, that the Johnson administration would not use the Gulf of Tonkin resolution as an excuse to expand the U.S. mission in southeast Asia, Nelson grudgingly voted for that August1964 measure. Only a pair of maverick senior senators, Oregon’s Wayne Morse and Alaska’s Ernest Gruening, opposed it. But, as Nelson came to realize that Fulbright had been bamboozled by the president, the Wisconsin senator joined Morse and Gruening in working to end the war.

In May 1965, when Johnson sought a $700 million supplemental appropriation “to meet the mounting military costs of Vietnam,” the Wisconsin Democrat broke ranks with the Democratic administration to join Morse and Gruening in opposing the spending measure. Speaking to the Senate, Nelson declared, “Members of the Senate, known as the world’s greatest deliberative body, are stumbling over each other to see who can say ‘yea’ the quickest and the loudest. I regret it, and I think that someday we shall all regret it.”

Noting that the administration had failed to make a compelling case that the war was necessary, let alone wise, the senator concluded, “Thus, reluctantly, I express my opposition to our procedure here by voting ‘nay.’ The support of the Congress for this measure is clearly overwhelming. Obviously, you need my vote less than I need my conscience.”

Nelson would continue for the better part a decade to be one of the Senate’s most passionate foes of the war. When the fighting was finished in 1973, he said, “Let us hope that our political leaders in both political parties have learned a lesson from this mistaken enterprise and will not involve the country again in a civil war where the vital interests of this country are not at stake.”

With U.S. troops stuck in the quagmire that is Iraq, it is obvious that the lesson was not learned. And the only way they will get out alive is if more senators learn the lesson that Nelson taught: Start talking about withdrawal early and don’t be afraid to vote your conscience.