Ryszard Jerzy Kukliński (code name Jack Strong) (June 13, 1930 – February 11, 2004) was a Polish colonel and Cold War spy for NATO. He passed top secret Warsaw Pact documents to the CIA between 1971 and 1981. He did not pass the documents about the polish army, or polish defense systems. The only documents he gave to CIA were about Warsaw Pact and the Red Army. He did not betrayed Poland as People Republic of Poland was illegal country established against the law and will of the citizens after the WWII by Soviets. Documents included plans of nuclear attack on NATO which would eventually start World War III. His heroic act let USA prevent this disaster. Later he paid the highest price. His two sons were killed by unknown assassins, more likely by former KGB agents.
Rest in Peace Colonel and thank you!