The evidence from recently declassified U.S. government documents is clear and compelling: There were American military prisoners held in the Soviet Union after World War II and the Korean War.

One such document, from U.S. Army-Europe headquarters in Heidelberg in 1954, recounts the testimony of a returned German prisoner of war who describes a man identified as Maj. William Thompson of San Antonio, an Air Force officer who told the German that he had been arrested by the Soviets in 1944 after a forced landing in Germany.However, Thompson's family was told in 1946 he was declared dead.

But the German informant, described in the document as "intelligent and cooperative," reported seeing and talking to Thompson in a prison camp in the early 1950s.

Another document, with the names deleted, describes two U.S. Army commandos and an Army lieutenant, captured in the Korean War and giving their names to other prisoners in the camps where they worked in the 1950s. The other prisoners, either Poles or Germans, gave the information to the U.S. government. There it stopped, with the State Department and Pentagon citing national security and refusing to put the information out, even to the families involved, on the grounds that it contained classified information.

That infuriates the National Alliance of Families, a group of POW families, and Rep. John Miller, R-Wash.

"I'm skeptical that anything from World War II and the Korean War could compromise U.S. national security now," Miller said in an interview.

He introduced a bill in the 101st Congress requiring the U.S. government to let families of military men listed as missing or killed in action to look at their files. The bill did not make it to the floor in the last session.

"We ran out of time," Miller said, "But we're going to reintroduce it in the next session."

Miller, who has seen some of the information still classified, says, "There is substantial evidence in the 1950s and '60s - from U.S. government documents - that there were American prisoners in the Soviet Union."

He said that is not necessarily grounds for believing that those Americans are still alive now.

The reasons for the presence of the Americans in the Soviet camps were diverse and sometimes not easily explainable, given the change in atmosphere from the Stalinist times to the current thawing of the Cold War.

But the first batch of U.S. POWs apparently resulted from the fact that in the final days of World War II, U.S. and Soviet forces both overran German POW camps, with allied prisoners in them.

The general agreement between the wartime allies was that prisoners in those liberated German camps would be returned to the country of their origin, but U.S. authorities held back some Soviet prisoners who knew they would be executed by Stalin if they were to be returned. In retaliation, Stalin held back some American prisoners taken from the German camps.

In addition, some Americans reported to be alive in Soviet camps in the late 1940s said they were kidnapped in Germany by Soviet authorities and never knew why they were picked out.