Amateur historian Matthew M. Aid made news this spring by exposing a secret federal program to remove thousands of public documents from the National Archives. It turns out that Aid harbored a secret of his own.

Twenty-one years ago, while serving as a staff sergeant in the U.S. Air Force in England, Aid was court-martialed for unauthorized possession of classified information and impersonating an officer, according to Air Force documents. He received a bad-conduct discharge and was imprisoned for just over a year, he confirmed in an interview Monday.

Aid, 48, did not mention the incident when a Washington Post reporter interviewed him for a June profile. Aaron Lerner of Silver Spring, a Post reader whose wife, Rona, remembered hearing of the court-martial while working at the National Security Agency in the mid-1980s, recently obtained the records through a Freedom of Information Act request and provided copies to The Post last week.

Aid said Monday that what he did was wrong -- but not unpatriotic. The top-secret code-word documents in his dormitory locker related to his job as a Russian linguist, he said.

"I had the proper clearance for it, so it's not as if I stole anything," Aid said. "Basically, being a workaholic, I took stuff home with me. . . . My lawyers at the time told me that a decision had been made in Washington to make an example out of me."

As for impersonating an officer, he said: "I wrote a letter to a girl, and I was trying to impress her. And that's all I'm going to say."