Polish-born Colonel Ryszard Kuklinski, one of the United States' top Cold War spies, died in a Washington hospital Wednesday at the age of 74, local news agency PAP reported.
As a senior Polish military staff officer, Kuklinski passed some 35,000 top secret Warsaw Pact documents to the CIA between 1972 and 1981 before defecting with his family to the West.
"Kuklinski was an officer who devoted all his life to avoid a war in Europe," said former Polish defense minister Jan Parys.
A communist court sentenced Kuklinski to death in 1984 for passing intelligence to the United States which included communist authorities' plans to impose martial law in 1981 to crush Solidarity, the old Soviet bloc's first free trade union.
Poland overthrew communism in 1989, but the sentence on Kuklinski, who lived in Washington, was lifted only in 1995 and he was not fully rehabilitated until September 1997.
He visited Poland in April in 1998 and received a hero's welcome by the then right-wing government, which said that thanks to people like Kuklinski the country had regained independence after five decades of Soviet-imposed regimes.
Kuklinski was survived by his wife. While he lived in hiding under an assumed name for many years in the United States, his two sons died in unexplained circumstances.
According to Polish newspaper reports, one son disappeared from a yacht which was later found by the U.S. coast guard. The other reportedly died in a car crash.