At 75, Waldo H. Dubberstein was an "old war horse" of Washington's intelligence community, once one of the Pentagon's top Middle East experts, a neatly dressed career bureaucrat with a pencil mustache who favored Washington cocktail parties, usually with a young woman at his side.

A onetime Lutheran seminarian and antiquities scholar at the University of Chicago, he came to Washington in 1942 and parlayed his expertise in ancient Assyria into a 40-year career of analyzing the volatile world of Mideast politics, first at the CIA and later, from 1975 to 1982, with the Defense Intelligence Agency.

His tenure was so long--he stayed on well past normal retirement age--that by the end, some younger colleagues complained Dubberstein's acumen had begun to wear thin, that he was "trading on his laurels." He was "a survivor," a man with "corridor smarts the way other people have street smarts," says one who knew him. Mainly, his peers thought, he was harmless.

But skeptical U.S. prosecutors investigating convicted arms dealer and ex-CIA agent Edwin P. Wilson ran across another side of Waldo Dubberstein. Last month they charged that in 1977 and 1978, he had traded classified military secrets through Wilson to Libya ruler Muammar Qaddafi for money.

The day after he was indicted on charges of conspiracy, bribery and betraying his position of trust, Dubberstein was found dead of a shotgun blast to the head, an apparent suicide victim. "I am not guilty," said a note left for Dubberstein's lawyers. There were no final words for his wife, Marie, from whom he was separated, or for Renate Strelau, 32, a blonde, German-born woman who shared Dubberstein's Arlington apartment.

"He was a very tough, sincere person. I know for him to do this took an awful lot of courage," said Marie Dubberstein last week. His only child, John, a 33-year-old California physician, described his father as a "very loving man. We're very upset."

The allegations against such a high-ranking government official, who continued to have access to sensitive documents until March of last year, have disturbed the American intelligence establishment and shocked all who thought they knew Dubberstein--or "Doobie," as he was known among his old friends in academia.

"My wife and I were astounded when we heard it. It comes as a great shock, the least thing I expected," said a former colleague at the National War College in Washington where Dubberstein did two one-year stints on the faculty after his retirement from the CIA in 1970.

Prosecutors refused last week to reveal the contents of documents they said were compromised by Dubberstein. His alleged activities coincided, however, with some of the most momentous events in recent Middle East history: Anwar Sadat's historic trip to Jerusalem, border hostilities between Egypt and Libya and the successful conclusion of the Camp David summit.

While not downplaying the seriousness of the charges, some former intelligence officials said last week they doubted Dubberstein's alleged leaks had grave foreign policy implications. Rather, they said they viewed the case as an example of a valued employe who should have been retired.

"I attribute it to his hanging around too long," said Ray Cline, former deputy director of the CIA. "It sounds as though he became careless . . . . A key factor seems to be that he changed women, which tends to upset people . . . . It proves to me he was getting a little soft-headed."

Federal investigators were weighing last week whether Dubberstein's sudden death was indeed a suicide, taking a hard look at his alleged ties to Wilson, who is in prison and facing charges of plotting to kill people knowledgeable about his dealings in Libya.

"No known connections that could be sensitive are being taken for granted," says one federal prosecutor who acknowledges that Dubberstein's alleged motives remain a mystery. "Anybody who tells you they know the answer to that is giving you a bunch of garbage."

Defense lawyers, proclaiming Dubberstein's innocence and the needless tragedy of his death, are pressing the Justice Department to drop the case. Federal officials, faced with an unexpectedly touchy diplomatic problem, say they may still release what they call impressive evidence accumulated against Dubberstein during an 18-month investigation.

His lawyers "might have changed their position if they'd seen the facts," says William C. Hendricks III, deputy chief of the Justice Department's public integrity section.

Groping for an explanation, some colleagues remained unconvinced last week that an official of Dubberstein's stature and means would jeopardize his good name and the country's security for $32,000, the payment specified in the seven-count indictment. "That would have been postage stamps to Waldo," says one former acquaintance.

Dubberstein, a GS-15, made about $60,000 a year as a DIA analyst, supplemented by retirement benefits from his long CIA career. Prosecutors at Dubberstein's arraignment, saying they feared he might flee the area, estimated his assets at more than $200,000.

"He didn't need the money. We used to joke that he was collecting a tremendous amount of money in salary and pension," said Professor Ignace Gelb, a former colleague from the University of Chicago who kept in close touch. "Besides, he was very stingy. "

Whether Wilson was suspected of paying Dubberstein more money, prosecutors refused to say.

Some friends said they questioned whether Dubberstein's relationship with Strelau may have changed his life's course. "Cherchez la femme," said one former associate half-jokingly. Yet few friends said they knew much about the young woman, whom Dubberstein apparently met at a conference on Middle East affairs in the mid-1970s.

Strelau, who appeared twice before the grand jury investigating Dubberstein, has declined to be interviewed.

According to academic records and other sources, Strelau was born in West Berlin, grew up in the United States and graduated in 1974 from the University of California at Berkeley, where she majored in political science. She spent a year in Middle Eastern studies at the Johns Hopkins School of Advanced International Studies in the District, but left before earning a master's degree.

In 1974, she answered an ad for a position as a research assistant in the press and information section of the Iranian Embassy. One former embassy official and others said Strelau was paid $600 to $700 a month to help put together a monthly publication about Iran for American readers and compile digests for her superiors of American news clippings.

Acquaintances said Washington's endless round of receptions and cocktail parties seemed to suit the 5-foot-10-inch, 160-pound Dubberstein, who struck others as personable and garrulous, if abrasive at times. He was outgoing, even boastful in a profession that puts a premium on the well-guarded answer.

"He was always telling me inside stories of the type I didn't need," says one former National War College faculty member.

"He was a rather academic analyst, rather donnish in style. He was very talkative and very eccentric," said Cline, now at Georgetown University's Center for Strategic and International Studies. "He liked to shock people by voicing unusual opinions. He was one of those academic showoffs."

In interviews with colleagues spanning his career, Dubberstein emerges as a man with solid academic credentials whose post-war assignments placed him among the original analysts at the CIA when it was created in 1947. "I wouldn't say he was an outstanding analyst; he was a very typical area expert who knew his region very well," said Cline.

Born in Bellefont, Kan., in 1907, he went from St. Johns College to Concordia Lutheran Seminary in St. Louis, earning the credits that would have qualified him to be a Lutheran pastor. Instead, he pursued studies in ancient civilizations at the University of Chicago's Oriental Institute, earning a PhD in 1934.

Except for occasional archeological expeditions, he never traveled extensively in the Middle East or mastered Arabic, according to former colleagues.

In the early 1970s, between his years at the CIA and the Pentagon, he held one-year positions at the war college and the American Enterprise Institute, as well as a stint at the Justice Department's narcotics intelligence office. By 1975, he was back in intelligence work, still in good physical health and apparently loath to retire. In turn his superiors found little reason to force him out.

"He wanted very, very badly to continue . . . and I had no basis for saying he was not doing the job, so I simply let the situation run," said retired Gen. Samuel Wilson, who was director of DIA from the spring of 1976 to August 1977. "He was an old war horse who didn't want to go off and be idle. At least that was my impression."