It’s no secret that Mad Max: Fury Road was an incredibly tough shoot. It’s also no secret that the film’s stars, Charlize Theron and Tom Hardy, didn’t exactly get along while making the film. All’s well that ends well, and Fury Road turned out to be a straight-up masterpiece, but while both Theron and Hardy have been largely complimentary about the finished product and George Miller’s direction, they’ve only coyly alluded to why they didn’t get along while making the film. Now, however, the two are opening up about what exactly drove them apart during the tumultuous shoot of Fury Road.

As part of an absolute must-read oral history of the making of Mad Max: Fury Road in the NY Times, Miller and his cast got candid about how rough the film was to make. They were not only secluded in the Namibian desert for months on end, crammed together inside of cars for much fo the time, but they also didn’t quite understand Miller’s vision for the film. It’s easy in hindsight having seen the finished product, but imagine having someone describe to you what, exactly, Fury Road is before it exists. It doesn’t follow conventional narrative storytelling, and is driven largely by action as it’s one long pursuit from start to finish.

Action is notoriously monotonous to shoot—you have to shoot three seconds of footage here, 10 seconds of footage there, and at the end you piece it all together and it looks thrilling. But actually making action isn’t all that fun. Now imagine that’s your entire movie. Not a good time! And Theron admits she didn’t entirely understand Miller’s vision while in production:

“The biggest thing that was driving that entire production was fear. I was incredibly scared, because I’d never done anything like it. I think the hardest thing between me and George is that he had the movie in his head and I was so desperate to understand it.”

Putting all of her trust in Miller was easier said than done, based on past experiences:

“All of those young girls kind of turned to me as someone who would problem-solve for them, and this is not anybody’s fault — I only say this now because I know George and I’ve experienced this with George, so I’d fully trust him. But I’ve also trusted directors fully when I didn’t comprehend what they were trying to do, and it just turned into a mess.”

Indeed, Hardy says in the NY Times piece that they basically just had to trust that all of this was going to make sense in the end, because the process of shooting it was tough:

“Because of how much detail we were having to process and how little control one had in each new situation, and how fast the takes were — tiny snippets of story moments were needed to make the final cut work — we moved fast, and it was at times overwhelming. One had to trust that the bigger picture was being held together.”

Because of their frustrations over not fully understanding the film that was being made, Theron and Hardy took some of their anger out on Miller, who himself admits in the piece that he “probably should have paid more attention to” the actors’ working process. Zoe Kravitz recalls to the NY Times that Hardy especially would lay into Miller:

“Tom really had moments of frustration, of anger. Charlize did, too, but I feel like he’s the one who really took it out on George the most, and that was a bummer to see. But you know, in some ways, you also can’t blame him, because a lot was being asked of these actors and there were a lot of unanswered questions.”

Theron says that in looking back on it, both she and Hardy were scared but neither communicated that to the other:

“In retrospect, I didn’t have enough empathy to really, truly understand what [Hardy] must have felt like to step into Mel Gibson’s shoes. That is frightening! And I think because of my own fear, we were putting up walls to protect ourselves instead of saying to each other, ‘This is scary for you, and it’s scary for me, too. Let’s be nice to each other.’ In a weird way, we were functioning like our characters: Everything was about survival.”

Hardy concurs with Theron's assessment:

“I would agree. I think in hindsight, I was in over my head in many ways. The pressure on both of us was overwhelming at times. What she needed was a better, perhaps more experienced, partner in me. That’s something that can’t be faked. I’d like to think that now that I’m older and uglier, I could rise to that occasion.”

Again, all's well that ends well, and both Theron and Hardy would go on to heap immense praise on Miller and the finished product, but these comments shed some light on exactly why tensions were running hot on the set. This wasn’t a simple case of one person being an asshole to another person. It was a group of people trying to help execute a groundbreaking vision that was nearly impossible to explain.

Kravitz sums it up nicely by saying she’d go back and do it all over again in a heartbeat, but that doesn't mean it wasn't one of the most challenging experiences of her life:

“As an actor, you make a lot of movies — some of them are good and some of them are bad, and you have to kind of let that go. But with this one, it really felt like we put our actual blood, sweat, tears and time into it, and if it hadn’t been good, I would have been devastated. It was one of the hardest things I’ve ever done in my life, but it was absolutely worth it, and I would do it again if George asked me to.”

For more on the making of Fury Road, head on over to the NY Times to read the full oral history.