“His anger drove him to become the most successful and valued agent the CIA had run inside the Soviet Union in two decades. The documents and draw­ings he passed to the United States in the early 1980s unlocked the secrets of Soviet radar and revealed sensitive plans for research on weapons systems a decade into the future. His espionage put the United States in position to dominate the skies in aerial combat and confirmed the vulnerability of Soviet air defenses—that American cruise missiles and bombers could fly under the radar.” The Atlantic has more about spy Adolf Tolkachev.