Igor Gouzenko

The case that told the West its wartime ally was already spying on it. Gouzenko was a cipher clerk at the Soviet embassy in Ottawa, and on the evening of September 5, 1945, he walked out with secret documents hidden under his coat. Canada's prime minister, Mackenzie King, set up a royal commission to examine them, and in February 1946 police arrested more than a dozen suspected spies. The episode is often called the start of the Cold War in the public mind, though historians differ on how much credit one defector deserves. It also shows the cost at home: the commission was allowed to set aside ordinary rules of evidence and deny suspects a lawyer.