"On September 5, 1945, Russian cipher clerk Igor Gouzenko walked away from the Soviet Embassy in Ottawa, Canada, with his pregnant wife and two-year-old son in tow. Contacting local authorities, he alleged that a military espionage network was operating in North America. His defection, occurring only a few weeks after the U.S. dropped two atomic bombs on Japan, sent shockwaves through Washington, London, and Ottawa." "Using newly declassified intelligence files, memoirs of eye-witnesses, and interviews with key players, Cold War scholar Amy Knight explains how this historic defection propelled Western governments into a feverish hunt for Soviet spies and a breakdown in relations with the Soviet Union." "In How the Cold War Began, Amy Knight chronicles a nearly forgotten but seminal episode from the early days of the Cold War, which occurred just as the Truman Administration was planning to remove stewardship of the atomic bomb from control of the War Department and place it under a civilian commission reporting to the president."--Jacket.