If William S. Lind advertised, which he does not, he would describe his services this way: "Upsets apple carts, rocks boats, brings new ideas and generally shakes things up."

That is the calling card of a gadfly. Washington has never been an especially hospitable place for the species, but still they come.

And comes now Bill Lind, a strange and curious subspecies. To mangle the mother tongue, he may well be the nation's capital's only switch-hitting gadfly.

Lind works part time for Sen. Gary Hart (D-Colo.), on whose staff he has toiled for a decade, with whom he has just cowritten a book ("America Can Win," Adler & Adler) full of smart-bombs aimed at the military establishment, but for whom he wonders whether he could ever vote.

And he works part time for Paul Weyrich, president of the Free Congress Research and Education Foundation, director of the Free Congress Political Action Committee and one of the leading conservative activists in the land.

Hart and Weyrich. If there be an odder couple, step forward, please. "People say he's either got one or both of us fooled," mused Weyrich. "In fact, it's neither . . . . He has caused me to think more deeply about different issues in different ways, and given me more philosophic insights than anyone I have around me . . . . You have to be quite unique to pull off what Bill has pulled off."

In the service of the liberal Hart, Lind has spent a decade taking on the military brass, whom he accuses of being "milicrats" rather than warriors, of building weapons that belong in museums rather than on battlefields, of asking the wrong questions, teaching the wrong courses, pushing the wrong doctrine and fighting the last war. How to clean up their mess? Begin, write Lind and Hart, by getting rid of 50 percent of all officers in all the services from the rank of major/lieutenant commander on up.

In the service of the conservative Weyrich, Lind has loosed an equally vitriolic attack on the Reagan administration -- from the right. He says it has been "an enormous disappointment to any conservative interested in anything more than getting rich." He says it has been "trivial." He says that the gravest threat the nation faces is the decline of the values, ideas and ways of life that Western civilization has developed over the last 300 years, and that the Reagan administration has failed to use its bully pulpit and moral suasion to halt that decline. He calls himself a "cultural conservative" and writes that "conservatism has rightly been described as a democracy that includes the dead." He predicts that the "next wave" of political energy will center not so much around the quest for new ideas as for old values.

One does not toss poison darts this way without attracting critics. Lind's targets at the Pentagon dismiss him as an "armchair strategist." Even his friends wonder whether his abrasive style isn't counterproductive. "Bill is a very impatient young man, and impatient young men don't take time for finesse," said Norman Polmar, a fellow military reformer.

Another associate, speaking on the condition that he not be named, was more blunt: "Bill likes to think that the young officers in the military are ready to take up his cause. And that might be true, except that he comes off as such an arrogant jerk that he turns off the very people who would be his allies. It's almost as if he's afraid his ideas will lose their integrity if they are embraced by anyone serious. So he's ever the gadfly. It is a kind of indulgence."

Lind scoffs at the suggestion he is his own worst enemy. "This town is cursed with an elaborate Spanish courtesy," he said. "It is considered improper here to call an idiot an idiot."

A baby-faced 38, Lind grew up comfortably middle-class on the west side of Cleveland, the son of an advertising executive. At age 12, he began reading Clausewitz. He wanted to go to the Naval Aacademy "until I read the course catalogue and discovered there was nothing in it about warfare. It was full of the two things I hate most -- sports and math."

Lind went instead to Dartmouth, where he majored in history, and then on to Princeton, where he did all of his course work, but not his dissertation, for a doctorate in European diplomatic history.

From there he went to work on Capitol Hill, first for Sen. Robert Taft Jr. (R-Ohio), and when Taft was defeated in 1976, for Hart. He does not find it anomalous that a staunch conservative should work for Hart. "I want to help rebuild the defense consensus destroyed by Vietnam," he said, "and to do that, you have to work on a bipartisan basis."

Lind's academic background and lack of military credentials have attracted notice. Last year he published the "Maneuver Warfare Handbook," a manual on how to train for and conduct battles. Retired Marine Corps colonel John C. Studt wrote in the introduction: "The author of this book has never served a day of active military duty, and he has never been shot at, although there are no doubt some senior officers who would like to remedy the latter deficiency.

"Yet," Studt continued, "he demonstrates an amazing understanding of the art of war, as have only a small handful of military thinkers I have come across in my [31-year] military career."

Indeed, given this background, Lind has burrowed notably deep into the collective psyche of the military. He is a frequent contributor to military journals and guest lecturer at military war colleges. He observes and gives formal critiques at military war games. In the early 1980s, he taught a regular course on amphibious warfare to Marine captains at Quantico until he found himself on the outs with the Marine high command.

What are the tenets of maneuver warfare? Lind uses one analogy to judo -- making the enemy's weight work against him. And another to football -- comparing it to a screen-pass play, when you let the enemy break through your line and then attack his rear flank. But the doctrine extends well beyond battlefield tactics; it goes to weapons systems and personnel practices as well. For example, he is distrustful of high-tech weapons, because he thinks they are too complex for the ever-changing circumstances of war. And he and Hart for years have been calling on the Navy to build more submarines and fewer aircraft carriers. In a showdown between carriers and subs, they say, subs win.

The Navy has steadfastly ignored the Lind line, and there are no major weapons systems in any service that bear the reformers' stamp. On the other hand, the Army and Marines have embraced elements of maneuver warfare in their training and doctrine -- though the colonels and generals say it would have happened, thank you, without any prodding from Lind and friends.

What next for Lind? Associates say he has had considerable influence on Hart's thinking on military affairs, but he says he can't envision himself in a major administrative position in a potential Hart administration.

It's not, he says, what he does best. Indeed, there is a piece of him that feels out of sync with his time and place.

He says he spends his free time (he's unmarried) "hunting for anachronisms." His hobby is "collecting third-rate Edwardian novels" and his passion is trolley cars. Every year since 1973, he and Weyrich have chartered a trolley in some city on the continent and thrown a big bash for friends.

He says he "lives to eat rather than eats to live," and notes that his "idea of a physical-fitness test is six eclairs in five minutes."

He is a Germanophile and, he confesses only part in jest, a bit of a monarchist.

"If the American people could ever see, up close, the way their government works, I guarantee you that George III would be back by popular demand in 24 hours," he observes.

Which would be okay by Lind: "I always wanted to live in the 18th century."