On the night of 2 June 1919, bombs went off in seven American cities. In New York the target was a municipal judge; in Cleveland, the mayor; in Pittsburgh, a federal judge and an immigration official; in Boston, a local judge and state representative; in Philadelphia a church; in Paterson, New Jersey, a leading local businessman. And in Washington, DC, a young man blew himself up outside the house of the US Attorney General, Alexander Mitchell Palmer, who was then seen as notably progressive. The explosion shook buildings across the capital; across the street, the young Franklin Roosevelt gaped in horror as the front windows of his house shattered. This was ‘class war’, read an anarchist pamphlet afterwards, printed on pink paper, ‘and you were the first to wage it … There will be bloodshed … We will destroy to rid the world of your tyrannical institutions.’ Within hours, the FBI was on the case.

As Tim Weiner argues in his new history of the crime-fighting bureau, a thick vein of paranoia ran through its history from the very beginning. The FBI was born at the turn of the twentieth century amid an atmosphere of severe labour unrest, anarchist terrorism and middle-class suspicion. ‘The time