What is McGovern-Hatfield Amendment?

Legal Definition
The McGovern–Hatfield amendment (alternately, Hatfield–McGovern amendment) was a proposed amendment to an appropriations bill in 1970 during the Vietnam War that, if passed, would have required the end of United States military operations in the Republic of Vietnam by December 31, 1970 and a complete withdrawal of American forces halfway through the next year. It was the most outstanding defiance of executive power regarding the war prior to 1971. The amendment was proposed by Senators George McGovern of South Dakota and Mark Hatfield of Oregon, and was known as the "amendment to end the war."

The amendment was heavily opposed by the administration of President Richard Nixon. A revision of the amendment intended to gain more widespread support extended the deadline for withdrawal to the end of 1971. Nevertheless, the amendment was opposed by Nixon and his backers in the Congress, who argued that a withdrawal deadline would devastate the American position in negotiations with North Vietnam. On September 1, 1970, the amendment failed by a 55–39 margin.
-- Wikipedia