The USSR and East Germany proved especially successful in placing spies in Britain and West Germany. Moscow was largely unable to repeat its successes from 1933 to 1945 in the United States. NATO, on the other hand, also had a few successes of importance, of whom Oleg Gordievsky was perhaps the most influential. He was a senior KGB officer who was a double agent on behalf of Britain's MI6, providing a stream of high-grade intelligence that had an important influence on the thinking of Margaret Thatcher and Ronald Reagan in the 1980s. He was spotted by Aldrich Ames a Soviet agent who worked for the CIA, but he was successfully exfiltrated from Moscow in 1985. Biographer Ben McIntyre argues he was the West's most valuable human asset, especially for his deep psychological insights into the inner circles of the Kremlin. He convinced Washington and London that the fierceness and bellicosity of the Kremlin was a product of fear, and military weakness, rather than an urge for world conquest. Thatcher and Reagan concluded they could moderate their own anti-Soviet rhetoric, as successfully happened when Mikhail Gorbachev took power, thus ending the Cold War.