For more than a half-century, they have kept an ear trained on the world, eavesdropping on the Japanese in World War II and the British more recently. But what they most want to hear now at the military spy listening post at Vint Hill Farms Station in Fauquier County is word of their own fate.

According to Sen. John W. Warner (R-Va.), it is believed to be the only Northern Virginia facility on the Clinton administration's list of military bases to be closed, which is scheduled to be issued today.

With the United States left as the world's sole superpower since the Soviet Union disintegrated, the Army intelligence installation outside Warrenton, about 35 miles southwest of Washington on the western border of Prince William County, no longer has the strategic importance it once did. "The demise of the Warsaw Pact in turn had an impact on the future of their mission," Warner said.

But it remains pretty important to the 2,500 soldiers and civilians who work there, as well to the local economy that benefits from the base's $84 million payroll.

"It's a substantial installation," said Georgia H. Herbert, chairman of the Fauquier County Board of Supervisors. "It's a significant part of the community in that many people hold civilian jobs there or had jobs there. There are more people in the community connected to Vint Hill than you would think."

Base officials would not comment yesterday.

Warner said the only other Virginia base at risk is an aircraft repair facility in the Norfolk area.

Warner and Rep. Frank R. Wolf (R-Va.), whose district includes the station, sent a letter to Defense Secretary Les Aspin Wednesday expressing concern about closing Vint Hill, particularly because of its secret operations.

Defense Department officials who have recommended closing the base, the congressmen wrote, "may not be fully aware of these important classified functions."

They wouldn't be the only ones. Vint Hill has been veiled in secrecy since the Army bought a 700-acre farm in 1942 and set up operations in a barn where the manure had just been shoveled out.

A thicket of sky-high antennae arranged in a diamond shape was set up and, according to a base historical account, was used in 1943 to intercept a message from the Japanese ambassador in Berlin to his superiors in Tokyo. It provided a detailed description of Nazi fortifications along the French coast. Gen. Dwight D. Eisenhower later said the information made a significant contribution to the Normandy invasion.

Today, the station is home to military intelligence units that develop and test signal equipment, conduct other research and support the operations of agencies such as the Central Intelligence Agency and the Federal Bureau of Investigation.

A study prepared for a congressional panel in 1977 said Vint Hill routinely spied on British government radio transmissions between London and Washington. A 1982 book called "Puzzle Palace" quoted a Vint Hill founder as saying the antenna field was set up to pick up messages beamed to and from Washington embassies.

Because of the station's history, the Fauquier Chamber of Commerce is working to establish a National Intelligence Museum there. While Vint Hill is relatively small compared with other Virginia military bases, it has played a large role in the local community.

About 835 military personnel, 1,200 civilian government workers and 400 to 500 employees of private contractors work there; 814 of their children attend local schools, according to Warner's office. And 570 reserve troops report there. Many children in Fauquier learned to swim in the base pool, and the officers' club is the site of many weddings.

Vint Hill has faced possible closing before and escaped, once in the early 1980s and again at the end of the decade.

This time, though, it will shrink even if it is not closed. The 201st Military Intelligence Battalion, made up of 383 soldiers, already has been ordered to relocate to Fort Gordon in Georgia beginning this fall.

To outsiders, Vint Hill may be an enigma. Not so to those who live nearby.

"Everybody knows somebody who's worked there and that takes away some of the mystery," Herbert said. But, she added, "I've never had anybody associated with Vint Hill Station tell me anything about their job."