The Third Battle of Yorktown is raging.

The first battle, in 1781, brought the American Revolution to a close.

In the second, in 1862, the Confederates yielded to Union Gen. G. B. McClellan's siege.

In the third battle, taking place now, Yorktown, Va., is fighting for its history.

The enemy, of all things, is recreation.

Historic conservation forces are supposed to be supported and funded by the federal Heritage Conservation and Recreation Service (HCRS). So is a needless recreation beach which, in Yorktown, obstructs proper conservation.

Asked to comment, HCRS' associate director for cultural programs, Hope Trumbull Moore produced two memos from anonymous HCRS field officers. One stated that Yorktown raised the dispute only because it is in financial trouble.

Yorktown's lawyer, William R. Harris, who last month filed Yorktown's complaint in U.S. District Court against the Interior Department, which is in charge of HCRS, said, "There is often an invisible conflict of interest between conservation and recreation."

Mary Matthews, owner of Nick's Seafood Pavilion in Yorktown and a member of the board of trustees does not think the conflict is invisible at all. "This is a national historic park, registered," she said. "Yet, right at Ballard Street Historic Landing, right where the patriots spilled their blood, I see not a historic marker but toilets and bath houses. They just grabbed that beach.

"People come here from thousands of miles. They come from Europe. They come with the Olympic torch, which runners carried to Lake Placid. They come here to see history, where we won freedom. They come to pay tribute to our national heroes. And what they see are toilets and bath houses," Matthews continued.

"The Yorktown commons is a national shrine," she said over the telephone from Florida, where she is vacationing. "It's as important as the Liberty Bell. But it's an eyesore, full of drifters with no respect for history, just having a good time fishing, singing, dancing all night. Now we have police patrols.

"You can't mix this kind of recreation with history," Matthews said. "I know, because I learned history and love for my country in Greece, when I was 6 years old. Now I fight for the history of my new country. I want young Americans to learn about the past so they can understand the future."

Thanks to an extensive computerized social history program, known as the "York County Project" and financed by the National Endowment for the Humanities, Americans may soon know a great deal about the daily life of an estimated 60,000 colonists -- from slaves to plantation owners -- who settled in Yorktown, Williamsburg and elsewhere in York County.

There is much evidence, furthermore, that serious archeological work on the Yorktown river front would yield important remnants of one of the most important ports of the colonies, its wharfs, warehouses and sunken ships.

Ignoring this evidence, much of which is documented in Yorktown's National Park Service library, the Heritage Conservation and Recreation Service approved and funded a public recreation beach.

The Service, according to the Yorktown trustees' court action, spent one day digging a shallow ditch, charged the town $792 and declared "it is virtually certain that nothing of historic value remains."

The Historic Conservation and Recreation toilets and much vandalized bathhouses now block the old commons public "wayes." When they were built, two Yorktown witnesses swear, foundations of old bricks and pegged planks from the colonial period were being destroyed. The archeological remnants were carted off to the town dump.

HCRS field officers claim that only two bricks were involved, one of them of recent vintage.

The federal agency, however, never made the environmental impact statement required by federal law.

Like most battles the Third Battle of Yorktown is a little confused and confusing.

The town today is only a village of less than 400 inhabitants whose board of trustees was established in 1691. It has not acquired perfect wisdom in these 289 years.

In fact, the board originally asked for a beach or something. It wanted to have its commons spruced up for the Bicentennial. Egged on by the county, unaware that the waterfront commons is a registered historic landmark, they had visions of lucrative concessions, motels and restaurants.

"Miss Mary" Matthews, with her Hellenic legacy of patriotic pride, however, thought history more important than hamburgers. Assisted by Harris, an international lawyer with a passion for the national heritage, Matthews now leads Yorktown's historic battle.

So far HCRS hasn't taken Yorktown's request for a few thousand dollars worth of serious archeological test digs too seriously. It seems to favor recreation over preservation. For every dollar spent on conservation, it spends three on recreation programs. The reason is obvious: Local businessmen and politicians see more profits in recreational developments.

In Yorktown, in Charleston, S.C., in Newbury, Mass., and in other historic preservation battle fields, HCRS has sided with the business interests which consider historic conservation an obstacle to progress.

The fact that historic and cultural ambience can, in the long run, bring as much, if not more revenue and tourism, is still kept secret in the Pension Building, where HCRS is headquartered.

Another complicating factor in the Yorktown case as elsewhere, is that the regional and field offices of the various federal agenies are willy-nilly scattered all over the landscape. Yorktown's Park Service Visitors Center is administered from Atlanta. Its recreation papers are shuffled in Philadelphia. Archeological services come from Boston. The decision makers are in Washington.

President Carter's reorganization has not yet organized this confusion.

All this has prompted a new impetus to bring order and more strength to the nation's efforts to conserve its heritage.

Rep. John Seiberling (D-Ohio) has introduced a bill that would give the historic preservation movement a federal agency of its own. While still within the Interior Department, the preservationists would have neither an overbearing Smokey the Bear to contend with, as they did when they were under the National Park Service, nor would they be buried under recreational beaches.

Another bill, introduced by Rep. Philip Burton (D-Calif.) would combine the administration of programs on behalf of the natural environment with those concerned with the cultural environment.

The Burton bill is supported by the newly formed American Heritage Alliance, which includes the National Trust for Historic Preservation, the Nature Conservancy, the Sierra Club, the Conservation Foundation, the Wilderness Society and other like-minded organizations.

The alliance promises new preservation power. That should help not only in Congress but also make the executive agencies execute natural and cultural preservation programs more efficiently and intelligently.

We need a strong force to win another victory at Yorktown.