There’s probably no sport harder to film than boxing. Any studio can get the best script, cast A-list stars, and hire a top-tier director, but if that fight choreography isn’t up to snuff, the audience will see right through it. No amount of camera trickery or quick cuts can hide a plodding bout with weak-willed punches getting thrown, after all.

That’s part of the reason why the Rocky movies have endured for decades—the attention to detail in those fights made every jab feel real, which helped heighten the tension and gave those bouts a real sense of urgency. It’s no accident, either. Those fights were painstakingly laid out from the script stages all the way through the intense choreography and into filming.

”There were 14 pages of left, right, right, left, left hook,” Stallone told The New York Times of the Rocky script back in 1976. ”What looked like haphazard throwing of punches was an exact ballet.”

Below, you can check out footage of Stallone and Carl Weathers—who played rival Apollo Creed—putting together the choreography for that first Rocky fight. And pay close attention to the details as Sly makes his vision clear, down to each individual punch thrown.