During the 30's we had a federal agency to deal with everything except intelligence. Russia had an international espionage network similar to the KGB and the UK had it's own espionage network. A good reference is "In the Garden of the Beasts" by Erik Larson (2011), a true story of love, terror and an American family in Hitler's Berlin. Ambassador Dodd was appointed by FDR in the mid 30's to be US ambassador to Germany. Dodd was unlike the usual rich club of ambassadors at the time. He was an idealistic liberal democrat college professor who thought he could make a difference in the deteriorating relationship between the US and the Hitler regime. After a year or two Dodd became desperate to inform the FDR administration about Nazi atrocities but nobody took the idealistic middle class college professor seriously. High ranking Nazis were escaping from Germany and any one of them would have been a prime source of information but sadly, the US wasn't interested. When the elitist network put pressure on FDR to relieve the idealistic ambassador in the late 30's he was replaced with an pro-Nazi more attuned with the international appeasement policy and the FDR administration thought Hitler would appreciate it and be our friend.