Legislation to expand the Manassas National Battlefield Park, which a former Virginia senator managed to hold captive in the Senate for most of his term, yesterday finally won that chamber's approval.

The proposal, opposed by former Sen. William L. Scott of Fairfax, won Senate approval yesterday largely because Scott's successor, Sen. John W. Warner (R-Va.), championed it.

The measure, passed on a voice vote, was an amended version of an expansion bill perennially sponsored by Rep. Herbert E. Harris (D-Va.) and approved by the House on five occasions. Yesterday's action must be confirmed by the House because the Warner-backed expansion is 900 acres smaller than the addition supported by the House.

Harris said yesterday that he was confident that both bodies can compromise, possibly as early as this week, and "we can have a bill on the president's desk at long last."

The Senate proposal also would cost less than the House-passed legislation, $8.2 million versus $21 million, largely because the Senate version calls for adding 815 acres to the park insead of the 1,715 acres that the House wanted.

Both versions call for inclusion of all of the historically significant land still outside the boundaries of the 3,000-acre park, which is located near Interstate Rte. 66 along the Prince William-Fairfax County border. Three historically important areas to be incorporated in the expanded park are Stone Bridge and the Wheeler and Brawner farms.

The primary difference between the two versions of the legislation is that Harris sought to purchase nearly 900 acres at the entrance to the park, as a buffer between the rolling parkland and the rapidly expanding commercial area of nearby Manassas.

In past years, opposistion to the expansion came not only from Scott, but from the state's senior senator, Independent Harry F. Byrd Jr., and the Prince William Board of Supervisors. This year, both Byrd and the county board testified in favor of the expansion.

Sen. Dale Bumpers (D.-Ark.), chairman of the Senate subcommittee on parks, recreation and renewable resources, observing both Warner and Byrd's support at a hearing Sept. 3, pledged to work for its passage, and he did. The full Senate committee approved the measure at a meeting on Sept. 17.

The park is the site of the first and second battles of Manassas, which were fought in 1861 and 1862. The first battle was the initial, major land battle of the Civil War. The second battle, lasting three days, caused the heaviest casualties of the war up to that time, and resulted in a Confederate victory that allowed Gen. Robert E. Lee to mount his first offensive campaign in the north.

The legislative fighting over the proposed expansion was so intense that politicians and editorial writers dubbed it "The Third Battle of Manassas." p