The Armed Services Committee was not exactly the assignment the self-described South Carolina country lawyer imagined for himself when he arrived as a House of Representatives rookie in 1983.

He tried to find his way onto Energy and Commerce, to no avail. He would have loved a spot on Ways and Means, but no go. Armed Services was where a spare seat awaited 40-year-old Democratic Rep. John M. Spratt Jr.

"You could understand why people weren't exactly enthralled with the subject matter," Spratt recalled, "because the hearings were dull as dishwater."

From those beginnings, fueled by a puzzle-solver's patience for detail and an education fancier than he readily lets on, Spratt has become an expert on U.S. nuclear policy and one voice among a devoted few on Capitol Hill sounding the alarm about atomic danger.

Now, talking about weapons design, he says things in casual conversation such as, "You've got the HE's side-by-side with the RVs." (Translation: High explosives are close to the reentry vehicle.)

He also says, "The threat of a fire next time, a nuclear incident, is real enough that we should be devoting much more attention."

When Spratt, the House Budget Committee's senior Democrat, examines President Bush's nonproliferation budget requests, he sees an approach he calls "politically correct" but "not aggressive at all. You don't get the impression that it's being pushed as a big priority."

Bush administration officials dispute that assessment, of course. Last week, Energy Secretary Spencer Abraham announced $450 million in spending over the next decade to retrieve enriched uranium from around the world.

But the polite and amiable Spratt is politely and amiably unimpressed. He figures that "in a budget growing this fast" -- defense spending has grown from less than $300 billion a year to more than $400 billion a year -- "surely if you wanted, you could find more money for nonproliferation."

Daryl Kimball, executive director of the Arms Control Association, describes Spratt as "the most influential House Democrat on defense and nonproliferation issues." In January, he became assistant to the House Democratic leader.

Political science professor Robert Botsch of the University of South Carolina at Aiken, describes Spratt as a deficit hawk who is "not flamboyant. Quiet. But when it comes to talking about future generations paying for today's spending, he gets pretty exercised."

But Spratt, 61, is an accidental nuclear specialist. A history major from Davidson College who makes references to Talleyrand, he reached Congress at a moment when he was beginning to think his hopes for a House seat had passed. Six days before the primary in 1982, the incumbent dropped out and Spratt saw his chance.

"Frankly," he said one recent afternoon as he crossed Independence Avenue to the Capitol, "it's something I always wanted to do."

As a boy, he helped his father, a prominent Democrat in small-town York, S.C., with political campaigns. At York High School, Spratt was elected president of the student body. At Davidson, ditto. He won a Marshall Scholarship that sent him to Oxford, where he studied economics and politics. Then came Yale Law School and the Army.

The United States was in the thick of the Vietnam War in 1969 when Spratt received an ROTC commission as an Army captain. He spent the next two years stateside, working on the staff of the Defense Department comptroller's office, examining procurement troubles.

For the next dozen years, Spratt practiced law in York, where he also spent time as the county and school district attorney. He prospered, becoming a bank president and owner of an insurance agency in nearby Fort Mill. His brother-in-law is Hugh L. McColl Jr., former chairman of Bank of America.

Elected to Congress the day after his 40th birthday, Spratt landed in Washington as a provincial star without many connections, like the high school football captain who arrives at college to discover himself surrounded by others who were captains, too. He went to the Armed Services Committee, where the future chairman, Les Aspin (D-Wis.), looked out for him.

Spratt chaired a panel on President Ronald Reagan's Strategic Defense Initiative, better known as Star Wars, the precursor to the missile defense system. When a colleague returned to claim the panel's top job, Spratt needed to look for something new.

"You play the ball where it lies," Spratt said. "If I wanted to have a role, I had to go after things other people weren't flocking towards. I had to find something fairly esoteric, that was both justified and didn't ruffle too many feathers."

Nuclear weapons. Highly enriched uranium. Atomic testing. Combined with his interest in budget matters, Spratt had found his metier.

When Bill Clinton won the White House in 1993 and made Aspin his secretary of defense, Aspin offered Spratt the job as Army secretary. Spratt turned it down. After a decade on the job, Spratt felt he was drawing closer to a leadership role in the House and was not convinced that an Army secretary would have enough "power, authority, discretion."

These are frustrating times for House Democrats who face the iron discipline of the GOP leadership. Spratt's ire was triggered most recently when he tried to move $400 million, including a large sum from the missile defense program, into raises for senior noncommissioned officers and warrant officers.

"This was not just a 'gotcha' amendment. These guys are the backbone of an army," Spratt said. "I thought we needed to have that debate on the House floor."

His amendment failed to make it that far, a predicament he said would not have occurred in an earlier, more collegial time.

"I raised hell about it," he said.

And what happened next?

"Nothing," Spratt said. "The well of the floor ought to be a great national forum, a crucible where we grind out good ideas for the country. I'm afraid that's not what we have now."

Spratt is deeply troubled by the administration's follow-through on the president's nonproliferation pledges. A particular peeve is the administration's recent increases in spending on research into new atomic warheads. He believes a resumption of testing, despite repeated denials, is "on the horizon."

"What troubles me most," Spratt told a recent Arms Control Association gathering, "is the attitude this administration seems to take. This administration seems to believe that the United States can move the world in one direction while we ourselves move in a different direction."

He was dismayed last year when the administration and its allies repealed a restriction, coauthored by Spratt, that had banned research and development on new nuclear weapons with yields lower than five kilotons. He said the administration is "taking us back to somewhere where we were years ago and were thankful to have moved beyond."

Rep. John M. Spratt Jr. used a seat on the Armed Services Committee to develop his niche: U.S. nuclear policy.