FBI agents on a stakeout during a kidnapping case with a field phone, 1939. The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service of the United States, which serves as the nation's prime federal law enforcement agency. Operating under the jurisdiction of the Department of Justice, the FBI is a member of the U.S. Intelligence Community and reports to both the Attorney General and the Director of National Intelligence. During the "War on Crime" of the 1930s, FBI agents apprehended or killed a number of notorious criminals who carried out kidnappings, robberies, and murders throughout the nation, including John Dillinger, "Baby Face" Nelson, Kate "Ma" Barker, Alvin "Creepy" Karpis, and George "Machine Gun" Kelly.