Ryszard Kuklinski
Ryszard Jerzy Kukliński (June 13, 1930 – February 11, 2004) was a Polish colonel and Cold War spy for NATO. He was posthumously promoted to the rank of brigadier general by Polish President Andrzej Duda. Kukliński passed top secret Soviet documents to the CIA between 1972 and 1981, including the Soviet plans for the invasion of Western Europe. The former United States National Security Advisor Zbigniew Brzeziński described him as "the first Polish officer in NATO."
Source: Wikipedia