Fleetwood Mac's split with co-founding guitarist Peter Green was as sudden as it was confusing. For the first few years after their inception, Green had taken the blues and brilliantly twisted it into an often otherworldly creation via songs like "The Green Manalishi" and "Albatross." But issues with drugs, coupled with his general mental state – Green was later diagnosed with schizophrenia – derailed everything.

Cracks in Green's armor and doubts about his own future path were becoming evident with the writing of the song "Oh Well," which dealt with some pretty heady material: "Now when I talked to God, I knew he'd understand. He said, 'Stick by me, I'll be your guiding hand. Don't ask me what I think of you, I might not give the answer that you want me to.'"

Their era-ending tour of Europe included dates in Germany, as Fleetwood Mac set about promoting their third album Then Play On. Green was swarmed by a group of hippies who led the wayward soul away from his band mates. It seems what happened next had something to do with drugs, something to do with his preexisting mental state, and something to do with religion.

When it was over, Fleetwood Mac had lost its frontman.

"Certainly John McVie would fully blame an event in Germany where Peter took some more drugs and never really came back from that," fellow co-founder Mick Fleetwood said in the Green documentary Man of the World.

"John is, to this day, absolutely furious with these people," Fleetwood added. "We called them the German Jet Set. They captured Peter completely, and pulled him away." Former Fleetwood Mac guitarist Jeremy Spencer remembered Green's new friends looking "at the rest of the band in disdain. I don't know if it was musically. They didn't think we were quite in the zone or whatever it was."

Listen to Fleetwood Mac Perform 'The Green Manalishi'

Former Fleetwood Mac road manager Dennis Keane believes the group was some sort of cult. "That is what they do: They get you in and they strip you of your identity, of your money," Keane remembered. "The reason I say that is because, Peter Green was a prime man who's making millions – and he did give off this religious look."

Green was actually joined in this misadventure by second guitarist and songwriter Danny Kirwan, a member from 1968–72. "Both of them took acid," manager Clifford Davis said. "Both of them, as of that day, became seriously mentally ill."

Fleetwood admits, however, that "Peter was already set to leave Fleetwood Mac, pretty much. But, my God, this was like the final nail in the coffin." Fleetwood Mac would be changed forever. "For me," McVie confirmed, "that was the fork in the road."

Their tour continued forward following the incident in Munich, but all concerned could see what lay further ahead for Fleetwood Mac. Still, like so much surrounding Green's departure, a debate continues on whether this incident was the catalyst or merely a coincidence of timing.

"Pete and I were sitting together on the bus, and he said 'I've been meaning to chat with you," Davis recalled. "He said, 'I wanna leave the band.' I said have you told the band yet, he said no and I said, 'Well, I suggest that you do'. So he went up to the front and told the band that's what he wanted to do." McVie says he never tried to change Green's mind about leaving. "I just remember going, 'Oh shit!'" McVie said.

Management approached Jeremy Spencer to see if he could persuade Green to stay with Fleetwood Mac, but ultimately Spencer felt it wasn't his place to step in if Green had made up his mind. Peter Green finished out the tour and, by the end of May 1970, he was gone.

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