Chad Stahelski has done his share of action movies. The stuntman and film director has worked on The Crow and The Matrix trilogy, stunting for Keanu Reeves before directed the actor in his first three films of the John Wick trilogy. According to Entertainment Weekly, the recent installment of John Wick (John Wick: Chapter 4) kept Stahelski and Reeves working for “a hundred nights,” thanks to the many night scenes that take place in the film.

"Even the interiors we shot at night because we were on a night schedule,” explained the director.

One action sequence in a sea of complex ones, however, managed to keep Stahelski “up at night.” The director reportedly found the battle at Paris’ Arc de Triomphe “particularly tough.” Rather than closing down the frenetic and congested traffic circle around the city’s magnificent 1806 triumphal arch, these particular scenes required a massive battle in which Wick, several leading bad guys, a squad of henchmen and several trained stunt dogs fight across speeding ongoing traffic.

"There's no easy scene. There's no easy days,” explained Stahelski. “It's just how creative you get with problem-solving. But, logistically, the trickiest one was obviously the Arc de Triomphe. You can't just hope the dog doesn't get hit by a bus and hope your leads don't get run over."

Referring to the sequence as a “nice stress attack,” Stahelski revealed the complexities that audiences don’t see.

"What people forget is, it's not just [the actors and stunt people]... I've got two camera crews in the middle of that traffic” explained the director. “ I've got 50 stunt drivers from all over the world with five different languages. We're kind of rehearsing as we go because you just can't afford to have 300 cars in rehearsal four months out, so everybody's rehearsed in pieces, and then, on the day, you have to put all those pieces together, and then you really have to have faith that you can pull this off.”

Related: 10 Times Actors Almost Died from Their Stunts

A Climactic Absurdity That Pays Off

Scott Adkins - John Wick
Lionsgate

More than just the pragmatics of executing a successful scene, Stahelski revealed his worries about the safety involved: “How are we going to hit a dozen stuntmen in one shot? When you see those five guys all get hit by cars in the same shot without a cut, that's all real; we had to time that out with everybody. Those are five stuntmen taking the hits and five drivers timing it amongst 20 other drivers. If you want to give yourself a little bit of stress, that's a good way to do it.”

Adding to the climactic absurdity of the film sequence, Stahelski added “And if that doesn't get you, throw in a couple of dogs! And a bus! And if that still doesn't do it, have your lead actor drive 40 miles an hour in an open-door Barracuda against traffic! That's a nice stress attack."

John Wick: Chapter 4’s attempt to outdo itself as the most complex film of the action tetralogy opened in theaters this weekend to a franchise record-breaking $73.5 million opening weekend. Variety called it “one of the rare original properties to keep growing and improving upon the last, in terms of ticket sales.”