Lt. Col. Craig G. Coverdale sat riveted on the edge of his cot one night in Vietnam in January 1969 as incoming mortar fire attacked his battalion. He strained to hear where it was coming from, when the door of his bunker opened and a hand grenade was thrown under his cot.

The cot took much of the explosion, but Coverdale's calves were badly mangled and he almost lost his right heel. During the next three months, while recuperating in Japan, he was hospitalized with about 40 lieutenants, most of them half his age. He received a sobering education, hearing what the war was like at their level.

The lesson, Coverdale said, transformed him into a better battalion commander--and was part of an evolution that took him from West Point to Vietnam to the Arms Control and Disarmament Agency to a nuclear-freeze candidate for Congress in the 8th Congressional District in Northern Virginia.

Coverdale, 52, announced recently he planned to run for the Democratic nomination for the seat held by Republican Rep. Stan Parris. The former soldier was, he said, "absolutely terrified by the saber-rattling" of the Reagan administration.

While wrestling with the question of whether to run, Coverdale said, he kept remembering a statement made by the late Republican senator Everett Dirksen of Illinois during a 1963 Senate debate on the nuclear test ban treaty: "I don't want them to write on my tombstone, 'He knew and didn't care.' "

Coverdale had informed close friends only a few months earlier that he was thinking of leaving his $60,000-a-year job at the arms control agency to run for Congress. Most said they were surprised and warned him it would be an uphill battle, something Coverdale is the first to admit.

The announcement by Coverdale, who lives in Alexandria near the George Washington Masonic Memorial, surprised and puzzled many Democratic Party regulars, including some who have been eyeing the congressional seat. Former representative Herbert E. Harris and State Sen. Richard Saslaw (D-Fairfax), currently considered the unannounced leading contenders, say they know little about the former soldier. Coverdale knows all this. That, he said, is why he started his campaign a year early.

But he hopes that his No. 1 campaign issue, the nuclear arms race, will generate the grass-roots support that has grown in other parts of the United States in recent years. He seems undaunted by the vastness of the task, talking energetically about going door to door and methodically putting together a coalition of like-minded individuals throughout the district, which extends from Alexandria to southern Fairfax to Prince William and Stafford counties.

Friends say Coverdale, now graying and slightly balding, always has been aggressive, enthusiastic and a stickler for detail. Sgt. Maj. Michael Biskup, who served under Coverdale in Vietnam and is now assigned to West Point, said that when Coverdale returned to Vietnam after his injury and was put in charge of a battalion with high casualty rates, he went through each aspect of the operation trying to pinpoint the causes.

"He was meticulous in his operation. He just doesn't go off half-cocked," said Biskup, who was in one of Coverdale's three helicopter crashes, which earned him the nickname, "Crash Coverdale."

"Morale just changed," Biskup said.

Coverdale spent most of his adult life in the Army, winning numerous medals and citations for valor, including the Silver Star. His roots and most of his friends are in the military.

Family lore has it that as a young boy, his grandfather went into the Army during the Spanish-American War to avoid jail. He ended up a brigadier general in World War I on Gen. John Joseph Pershing's staff. His father was a West Point man, who was captured by the Japanese in China during World War II and escaped after being declared dead.

When Coverdale graduated from high school in 1948, he had his sights set, not on the Army, but on the Merchant Marine. "I really didn't want to do anything except travel around the world and be a free spirit," he said.

That changed when he was stranded that summer in California with no money and his father agreed to send him a bus ticket on the condition he enter military prep school. From there Coverdale proceeded to West Point, Fort Benning, Ga., Austria, Italy and Fort Campbell, Ky. In 1956 he left the Army to join a small tool and machine company, but missed the Army and returned within two years.

Coverdale became a specialist in Turkey, and while there volunteered for his first yearlong tour in Vietnam in 1966. He returned to Vietnam in 1968 to command a battalion.

When he was sent to Japan only a few months later to recover from the hand grenade injuries, Coverdale said he thought his "whole world had tumbled... I felt like I'd been cheated out of my battalion command, the thing I had spent my whole life preparing for."

At first he spent a lot of time alone in the hospital. There were no captains or majors, only lieutenants. "I didn't even talk to them," he recalled. "They were beneath my dignity or something. Then I got lonesome and I started talking to them, and they started telling me what the war was really like and what the really important thing was, which was saving lives while doing the mission."

Coverdale eventually took over another battalion in Vietnam, where he stayed until 1970. He then spent three years at the Defense Intelligency Agency and a year at the National War College. At both places he became increasingly convinced of the futility of a nuclear arms race and the feasibility of arms control.

"Arms control is a political problem, not a technical one," said Coverdale. He said that verification techniques, while not perfect, are impressive. In addition, he said, it is far easier for the intelligence community to monitor the activities of either side when a treaty is in effect. "It doesn't mean we have to trust each other," he said. "There's no trust involved."

In 1976, he was assigned to the U.S. Arms Control and Disarmament Agency. When he retired from the Army in 1978, he received a civilian appointment to the agency. The following year, Coverdale traveled the country for the government defending the SALT II treaty at high schools and chamber of commerce meetings. The treaty was never ratified.

"When the Reagan administration took office in 1981 there was almost a total cessation in positive arms control efforts . . . ," he said. "I became more and more alarmed by the posture of the Reagan administration." And that, said Coverdale, is when he decided to run for Congress.

"We're not talking about the Battle of Hastings now when we're talking about nuclear weapons," he said. "We're talking about the most severe holocaust that will have ever been visited on this planet and it will never again be the same after that event. The only cure is prevention."