The new super-stylized, ultra-violent action flick Atomic Blonde wastes no time with pleasantries. In the very first scene of the movie, a British agent running in his boxers through late-‘80s Berlin is smashed by a car and then executed point-blank by a laughing KGB agent, who then dumps his body into the river Spree. The action only intensifies from there, building up to a brutal series of extended fight scenes across East Berlin, including a remarkable sustained burst of hand-to-hand combat in an abandoned apartment complex.

Charlize Theron stars in the film as Lorraine Broughton, the titular atomic blonde, a hardened cipher of an MI6 agent. She’s a walking weapon, with advanced combat skills and a good eye for determining which household objects might best be used as makeshift lethal weapons. That very particular skill comes in handy during the long fight sequences in the East Berlin apartment building, which see Lorraine get the pulp beaten out of her while taking on a squad of KGB agents.

Director David Leitch thinks hard about action, as he was a stunt coordinator and second unit director for 20 years before making his directorial debut with John Wick. And he regarded this sequence as “the pinnacle of the action in the movie,” with its carnage serving a larger purpose than providing simple thrills.

“We planned to arc the action tonally with Lorraine’s journey,” Leitch tells Inverse. “[The movie] is fun in the beginning. You enter this crazy new world in Berlin, and you see her beat up some cops in a really fun Jackie Chan way, you meet crazy Percival (James McAvoy), and the music is fun and ironic. It’s a sexy world, but as the lies start piling up, the movie gets darker and darker, we wanted to have a set piece where we really sort of manifest her bigger physical and extensional crisis.”

The result is a long sequence that begins in the middle of a political protest — the movie takes place during the final days of the Berlin Wall — and then heads to the empty apartment building. A cold and utilitarian structure typical of Soviet architecture, it’s clear of people but still filled with their personal possessions, which came in handy as the fights got more desperate and scrappy.

The apartment building has four extended staircases connecting three floors, and Leitch decided that the camera would follow Lorraine as she descends from the top, stopping at each level — and sometimes on the steps — to throw down with her pursuers. Not everyone was immediately sold on the idea: “I’d presented it to my stunt team before, and everyone’s always kind of like cautious and hesitant, because [they asked] are you really going to be able to stay in it?” Leitch recalled. “Is it going to be compelling? Are you going to want to cut away for energy?”

The scene became more compelling and energetic because of the stakes: Lorraine is charged with protecting the life of a defecting Stasi officer code-named Spyglass, who holds vital information that could change the course of the Cold War, which seems to be winding down. And because Spyglass is no soldier, but instead a wimpy paper-pushing geek, he’s more of a burden than help (minus one clutch assist).

Every inch of the building had to be analyzed and an incredibly detailed production plan had to be mapped out; every punch, flip, blow to the head, gunshot, and furniture-busting body-toss required careful choreography. Shooting the apartment sequence took four days in total, not an unsubstantial chunk of time for a mid-budget movie shot on foreign soil (mostly in Budapest). It was far too much to realistically film in one continuous take, but careful planning allowed Leitch to give it that illusion.

“There are long, long pieces of choreography, and then there are sort of old school movie stitches, and then there’s a little bit of visual effects, and then there’s camera tricks,” the director says. “We’re stitching together different sections of it, but ultimately we shot it in order, so we could make sure that it all seamlessly worked as one shot.”

The longest continuous take in the movie lasted about two minutes, which is a huge number for such a complicated scene, with so many moving and exploding pieces. It’s a battle between Lorraine and a Russian assassin with a Macklemore-style haircut, and they beat the ever-loving hell out of one another: Lorraine stabs him with a corkscrew and clocks him with a large double record turntable (or a big hot plate, it’s hard to tell), while he tosses her around into wooden furniture that shatters on impact.

The long, continuous take is even more notable because Theron was in the arena herself, taking the punches and abuse that, while carefully staged, is punishing nonetheless.

“There are a few details where you just can’t risk slamming your actress ten times into a breakaway cabinet, so we found a way to graft in a stunt performer. But all the fighting, all the brutality in that fighting and the selling of fighting, it’s all her,” Leitch says.

It also helped that Theron was facing off against trained professionals. With two decades of stunt work and choreography under his belt, the director feels an allegiance to stunt performers and also believes deeply that, if it’s their ambition, they can transcend the category and do more on screen. And so, he cast actual stuntmen as the KGB agents in the stairwell, so that the fighting could be more authentic and expertly planned out; this way, he didn’t have to worry about training other actors for some shots and stitching their faces in digitally over stunt performers’ for others.

“It was crucial to the whole scene in that they could practice the choreography with her, and make subtle adjustments for camera and for her,” he explains. “We know that it’s going to be safe — they’re going to be the right distance and they’re not going to hit her. I’m not prejudice. I mean, if they can act and they can do stunts, then I’ll let them do both.”

Given Theron’s extreme training and action scenes, it’s clear that Leitch’s maxim goes both ways, resulting in some of the most intense, complicated fight sequences in recent studio cinema history.

Atomic Blonde hits theaters on Friday, July 28.