The Soviet Union conducted an extensive and continuous espionage attack against the security institutions—political, economic, and scientific—of the United States from the time of Washington's diplomatic recognition of the USSR by the Roosevelt Administration. <ref>Felix Wittmer, [http://www.geocities.com/Pentagon/6315/yaltabet.html ''The Yalta Betrayal''], Claxton Printers, 1953, p. 15. </ref> That attack continued not only during the time [[Molotov-Ribbentrop pact|the USSR was allied with Nazi Germany from 1939]] until it was [[Operation Barbarossa|attacked by Germany in 1941]], but during the war years 1941–1945 when the Soviet Union was one of America's main allies. The main thrust was to give impetus to the Soviet drive for [[World Revolution]]; to increase the political power of CPUSA, and to strengthen the Soviet economy by economic and scientific espionage. A major instrument of Moscow's policy was the CPUSA. | The Soviet Union conducted an extensive and continuous espionage attack against the security institutions—political, economic, and scientific—of the United States from the time of Washington's diplomatic recognition of the USSR by the Roosevelt Administration. <ref>Felix Wittmer, [http://www.geocities.com/Pentagon/6315/yaltabet.html ''The Yalta Betrayal''], Claxton Printers, 1953, p. 15. </ref> That attack continued not only during the time [[Molotov-Ribbentrop pact|the USSR was allied with Nazi Germany from 1939]] until it was [[Operation Barbarossa|attacked by Germany in 1941]], but during the war years 1941–1945 when the Soviet Union was one of America's main allies. The main thrust was to give impetus to the Soviet drive for [[World Revolution]]; to increase the political power of CPUSA, and to strengthen the Soviet economy by economic and scientific espionage. A major instrument of Moscow's policy was the CPUSA. |