I wrote about this last year and while it’s not exactly a secret it’s a story surprisingly few people know, so I think it’s worth repeating:

In November 1964, weeks before Martin Luther King was to travel to Oslo to receive the Nobel Peace Prize, an anonymous correspondent sent him a package in the mail. The package contained an audiotape, and a letter.

The tape was a compilation of material recorded via Bureau wiretaps over the previous year. It consisted of off-color jokes and remarks King had made in private, among friends, interspersed with the sounds of him having sex with someone other than his wife. The letter included the following challenge:

King, look into your heart. You know you are a complete fraud and a great liability to all us Negroes. … you are no clergyman, and you know it. … You could have been our greatest leader. You, even at an early age have turned out to be not a leader but a dissolute, abnormal moral imbecile. … You are done. Your “honorary” degrees, your Nobel Prize (what a grim farce) and other awards will not save you. King, I repeat you are done. No person can overcome facts, not even a fraud like yourself. … The American public, the church organizations that have been helping — Protestant, Catholic and Jews will know you for what you are — an evil, abnormal beast. So will others who have backed you. You are done.

King, there is only one thing left for you to do. You know what it is. You have just 34 days in which to do [it]. … You are done. There is but one way out for you. You better take it before your filthy, abnormal fraudulent self is bared to the nation.

The letter was mailed 34 days before Christmas.

King did not receive the package until after he returned from Oslo, and after the 34-day deadline had passed. When he listened to the tape he quickly concluded that it could have come from only one source — the Federal Bureau of Investigation.

He was right.

The FBI had been wiretapping King for over a year by then, and Bureau chief J. Edgar Hoover made no secret of his loathing for the civil rights leader. The suicide package was prepared by Hoover deputy William Sullivan, an Assistant Director of the Bureau and the head of its Domestic Intelligence Division.

When you teach American history as I do, you get asked about conspiracies a lot. As it happens, I’m skeptical about some of the biggest conspiracy theories out there — unlike nearly all of my students, for instance, I think it’s highly likely that Lee Harvey Oswald acted alone.

But I’m not one to ridicule such theories either, and I find the smug dismissal with which they’re so often greeted deeply obnoxious. Because forty-seven years ago one of America’s highest ranking law enforcement agents launched a secret campaign intended to blackmail the country’s most prominent civil rights activist into committing suicide.

That’s not a theory, it’s a fact. And once you know that, it gets a lot harder to dismiss other people’s stories of shadowy government goings-on.