1939 10 January Soviet intelligence defector Walter Krivitsky has the first of several debriefings at the Department of State. 26 June President Roosevelt secretly gives the Federal Bureau of Investigation (FBI), the Military Intelligence Division (MID), and the Office of Naval Intelligence (ONI) exclusive responsibility for counterespionage. 23 August Germany and USSR sign Non-Aggression Pact. 1 September World War II begins as Germany invades Poland. 1940 21 May President Roosevelt authorizes the FBI to conduct warrantless electronic surveillance of persons suspected of subversion or espionage; surveillance was to be limited insofar as possible to aliens. 5 June FBI-MID-ONI "Delimitation Agreement"...