The Senate confronts the issue of the War Powers Resolution again today when advocates of congressional intervention in the Persian Gulf military operation determine whether they have the 60 votes necessary to break a threatened Republican filibuster.

The vote will be on whether to limit debate, proposed by Senate Majority Leader Robert C. Byrd (D-W.Va.) and Sen. John W. Warner (R-Va.). The Byrd-Warner proposal makes no reference to the war powers law, but would require a vote in 90 days that could lead to modification or result in termination of the U.S. military's gulf operation.

The following covers the highlights of the law:

Background

The War Powers Resolution was approved in November 1973, when Congress dealt President Richard M. Nixon, who vetoed the law as "unconstitutional and dangerous to the best interests of our nation," a stunning setback. The House overrode Nixon's veto by 284 to 135 -- four votes more than the two-thirds majority necessary. The Senate followed -- providing the first successful reversal of a presidential veto in the 93rd Congress -- by voting 75 to 18 for an override.

At that time, critics of the Vietnam war charged that Nixon was exercising the power to declare war, which the Constitution gave solely to the legislative branch. Congress did not declare war in Korea or Vietnam.

No president since Nixon has acknowledged that the law is constitutional, but no president has challenged it in court.

Provisions

The law requires the president to notify Congress within 48 hours any time he sends combat troops into a foreign country or "substantially enlarges" the number of U.S. troops there. He must provide progress reports to Congress every six months.

If the troops are sent into hostilities, or into "situations where imminent involvement in hostilities is clearly indicated," they must be withdrawn after 60 days unless Congress declares war or authorizes them to remain.

The president can obtain a 30-day extension of the 60-day withdrawal deadline by certifying that "unavoidable military necessity" requires the troops to stay longer to ensure a safe withdrawal.

Previous Reports

Since its enactment, presidents have formally submitted 12 reports under the War Powers Resolution:

April 4, 1975. President Gerald R. Ford reported he had directed U.S. participation in an international relief attempt to transport refugees from Da Nang and other seaports to safer areas in Vietnam.

April 12, 1975. Ford reported use of U.S. forces to assist with the evacuation of U.S. nationals from Cambodia.

April 30, 1975. Ford reported use of armed forces to aid in the evacuation of U.S. citizens and others from South Vietnam.

May 15, 1975. Ford reported he had ordered U.S. forces to rescue the crew of and retake the ship Mayaguez, which had been seized by Cambodian patrol boats.

April 26, 1980. President Jimmy Carter reported use of armed forces in an unsuccessful attempt to rescue hostages in Iran.

March 19, 1982. President Reagan reported deployment of military personnel to the multinational force in the Sinai to assist in carrying out the peace treaty between Egypt and Israel.

Aug. 21, 1982. Reagan reported dispatch of 800 Marines to serve in the multinational force overseeing the withdrawal of Palestine Liberation Organization forces from Lebanon.

Sept. 29, 1982. Reagan reported deployment of 1,200 Marines to help restore Lebanese government sovereignty.

Aug. 8, 1983. Reagan reported deployment of two electronic surveillance planes, eight fighter planes and ground-support forces to assist Chad against Libyan and rebel forces.

Aug. 30, 1983. Reagan reported that Marine positions in Lebanon came under fire and two Marines were killed.

Oct. 25, 1983. Reagan reported on deployment of 1,900 soldiers and Marines in Grenada.

April 16, 1986. Reagan reported on air strike against Libya.

Sources: Congressional Quarterly, Presidential Documents, Library of Congress