In the summer of 2018, twelve boys aged 11 to 16, along with their soccer coach, became trapped in a flooded cave system in northern Thailand. What ensued was an 18-day rescue mission led by elite British divers John Volanthen and Richard Stanton, who found the boys alive but miles from the nearest exit and devised an elaborate plan to get them to safety, despite being underground, underwater and under the watchful eyes of the world.

All the while, more than 10,000 volunteers — including rescue workers, governmental officials and family members — came together outside the cave to pull off an impossible mission.

Thirteen Lives, director Ron Howard's feature dramatization of the Tham Luang cave rescue is a feat in itself. The two-time Oscar winner (Best Picture and Best Director for 2001's A Beautiful Mind) meticulously recreates the real events, including production designer Molly Hughes reconstructing the actual cave from scratch, and stars Colin Farrell and Viggo Mortensen (who portray Volanthen and Stanton, respectively) doing the diving for real.

It was the most demanding film of Howard's career. As told to A.frame, here is how he pulled it off.

William Nicholson's script surprised the hell out of me. I thought I knew the story — and I did know the headlines — but I did not know about so many of the controversial, difficult decisions that had to be made. I didn't understand the level of volunteerism and the way the volunteers made a difference, the way they moved the needle on behalf of these kids to make the dives and the hands-on rescue of the boys even possible.

In deciding if I would direct it, there were a number of factors that I weighed in, and I took a little bit of time. Because it was going to be a huge undertaking! But ultimately, I felt that the script was a gift, that this was a story that urgently needed to be made. The idea of this international group of volunteers making this miracle happen was an abject lesson in the viability and plausibility of maintaining hope, and I really wanted to be a part of bringing that to the screen.

I've done a lot of shooting of practical, precarious, real-world situations — whether that's an F1 track [2013's Rush], or it's weightlessness in space [1995's Apollo 13], boxing rings [2005's Cinderella Man], firefighting [1991's Backdraft] — and I felt like I could do something really cinematic, and intense, and suspenseful here that would be compelling, be entertaining, and also reveal, in a granular way, what's required to achieve something like that. And we could go much further thanks to the commitment of the real divers being our technical advisors, and our underwater team led by Simon Christidis, who is a world-class underwater photographer.

But there wasn't much time. Of all the movies of this scale that I've tackled, this was the least expensive and had the fewest number of shooting days. So, it was a marathon for me.

One of the most challenging days was what we wound up shooting on our very first day, for lots of logistical and scheduling reasons. It was the divers arriving in chamber nine and finding the boys. That's a pivotal scene. It raises the stakes of the movie because, on the one hand, they're thrilled when they realize that the boys are alive. But, on the other hand, they have no idea how they could possibly get those kids out alive. Now they're confronted with this idea that they may well witness this slow death, which is an agonizing prospect.

That sequence reflects so much of what was challenging about the movie. It starts with underwater scenes, with the divers having to authentically work their way through tight spots to get into that cave. I breathed a real sigh of relief when some of the really precarious dive scenes were done, not because I felt like somebody was going get injured. But I wasn't a hundred percent sure we could get the cameras into those tight spaces and get the details in order to make you realize that it's not just a matter of squeezing through. That your hand has to go first, and then, there's the tank, and you're not sure how much oxygen you have — there are so many factors.

I've got to give a nod to the actors, who not only learned to do the diving but became proficient enough that they did all their own diving. They implored me to let them do all their own diving. And, whenever they had a half a day off or a third of a day off, or God forbid, a full day off, they waved that and just went to the water unit. It became so relaxed that, at times, Simon would actually hand them a Mini Cam, which is much bigger than a GoPro, but it's a thing they can hold in one hand, and they would shoot themselves diving in some of these tight places. And shoot their buddy, and follow, and lead and things like that. That was great.

On top of that, it's these boys who had never acted before, because we had to get kids from Northern Thailand. That's a very specific dialect, and in order to have kids improvising — which I knew we would need — they needed to be able to use their own vernacular and accents. It was their first day of shooting, and it was really East meeting West in a very intimate, detailed, nuanced way.

I recognized that a big portion of the movie was going to be in Thai and the movie needed to very authentically reflect Thai culture in a way that not only respected the culture, but also reflected it in an honest way. I needed to be able to really transport people to that place. And I knew that was going to be a tremendous challenge and a bit of a risk, because I couldn't outrun that one. I couldn't just work so hard that I would know everything about Thailand to be able to get it right.

I love collaboration, but I was going to have to take that to another level of commitment and trust. And I recognized that I needed to implore the actors and the translators — Vorakorn "Billy" Ruetaivanichkul and Raymond Phathanavirangoon, who wound up becoming co-producers because they're very talented — to not let me step on landmines, to help this version of this story reflect a Thai perspective as much as you possibly could. I kept saying, 'I'd love it if Thai audiences watched the movie and kind of forgot that a foreigner made it.'

I don't know if I've achieved that or not, but that was the litmus test in my mind. That was the target. I'd gotten that wrong early in my career, and gotten it better as I've gone along, of directing scenes and characters not in my own language. Given that it is an international story, I thought I was as valid a choice as any. That maybe was when I breathed the biggest sigh of relief.

I was grateful for all my experiences leading up to this, including the documentaries that I've done in recent years. I think it all came together to be one of the most technically, and culturally, and dramatically challenging films I've ever made.

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