On April 27, 1979, the other members of Black Sabbath decided that they’d finally had enough of lead singer Ozzy Osbourne and his out-of-control behavior and showed him the door.

It was a stunning decision, one that hit Osbourne like a ton of bricks, as he recalled in his book, I Am Ozzy. “We were doing some rehearsals in L.A., and I was loaded, but then I was loaded all the time,” he remembered. “It was obvious that Bill [Ward] had been sent by the others, because he wasn’t exactly the firing type. I can’t remember exactly what he said to me … but the gist was that Tony [Iommi] thought I was a pissed, coked-up loser and a waste of time for everyone concerned."

In Iommi's memoir, Iron Man, the guitarist defended himself by writing, “Ozzy seems to think it was me who pushed it, but I was only speaking on behalf of the band and trying to get the thing going. Somebody had to make a move, somebody had to do something otherwise we’d still be there now and we’d all be out of it. So that was it.”

Iommi went on to describe the state of the band at the time of Osbourne's firing and the toll that drugs had taken on the group as a whole: “We had been together for a decade, but it got to a point where we couldn’t relate to each other any more. There were so many drugs flying around, coke and Quaaludes and Mandrax, and there was booze and late nights and women and everything else. And then you get more paranoid and you think, they hate me. We never fought, but it’s hard to get through to people, to communicate and solve things when everybody’s out of it.”

As shocking as the incident proved to be, ultimately it ended up working out more or less in everyone’s favor -- at least in the short term. Black Sabbath tapped a fellow named Ronnie James Dio to take over on vocals and together they made one of the group’s biggest and most well regarded records, Heaven and Hell. Osbourne -- in one of the most unexpected rebounds in rock history -- discovered a hotshot L.A. guitar player named Randy Rhoads on the way to crafting an incredibly successful solo career. He would soon go on to dwarf the popularity of the band who fired him despite still struggling with his addictions.

In later years, an increasingly rapid series of lineup changes left Black Sabbath in comparatively poor commercial standing. In 1997 they reunited with Osbourne for the first of what would be several times. In 2013 the group -- without Ward -- released their first full new album together in decades, 13, and the tour, billed as a farewell, ran through February 2017.