Semper Fie

Marine Sergeant Clayton Lonetree, 25, was so highly regarded at his job as security guard at the U.S. embassy in Moscow that in November 1985 he was detached for special duty at the Reagan-Gorbachev summit in Geneva. Last week Lonetree sat in a brig at the Marine base at Quantico, Va., suspected by his superiors of helping the Soviet KGB filch classified U.S. documents from diplomatic offices in Moscow and Vienna.

Lonetree, authorities said, had an affair with a female KGB agent who was reportedly working as a translator at the embassy. The woman took him home a number of times, introducing him to her "Uncle Sasha," who was actually a KGB agent. The translator had been among 260 Soviets employed by the U.S. embassy in Moscow and the consulate in Leningrad until the Kremlin pulled them out last October to protest Washington's expulsion of 80 Soviet diplomats.

Although Navy investigators are still assessing the damage Lonetree may have caused, Defense Secretary Caspar Weinberger said the case represents a "potentially serious set of intelligence losses." Among the duties assigned to the Marine guard, who served in Moscow from September 1984 until last March and then in Vienna until December, were checking empty offices for unsecured documents and disposing of "burn bags" containing classified material to be destroyed. Pentagon sources indicate that Lonetree not only provided the Soviets with secret papers but also told them the names of CIA personnel in the two embassies, detailed the work habits of the American staff members and sketched the layout of the Moscow and Vienna embassy offices. Eventually Lonetree felt trapped by his Soviet controllers and turned himself in to U.S. authorities in Vienna.

The son of a Winnebago Indian father and a Navajo Indian mother, Lonetree joined the Marines in 1980. In Moscow he was one of 30 guards at the embassy. Subject to strict rules of conduct about associating with Soviet citizens, the Marines are forbidden to leave the embassy alone without permission, although that regulation is sometimes skirted.

While military lawyers were considering possible charges to bring against Lonetree -- including espionage, which carries a possible death sentence -- the situation served to illustrate the continuing problem of security breaches by low-level personnel. Like Lonetree, Navy Yeoman Michael Walker, 24, convicted last year of sending classified material from the aircraft carrier Nimitz to his father, Soviet Spy John Walker, had easy access to sensitive documents: he too was on the burn-bag squad.