If Thor: The Dark World was a step in the wrong direction for Marvel Studios in trying to expand the MCU following Marvel’s The Avengers, then Captain America: The Winter Soldier paved the way for the future. Indeed, one could almost look at the Captain America trilogy as the narrative spine of the Marvel Cinematic Universe, and with The Winter Soldier Marvel delved deeper into the world these superheroes inhabited than ever before. The end result remains a fan-favorite film, one that pulled from a surprising tone and genre to forge a path forward that would upend the MCU forever.

Given that Captain America is, well, Captain America, Marvel already began preliminary work on a sequel before Captain America: The First Avenger was released. The studio brought back writers Christopher Markus and Stephen McFeely, who initially considered littering the sequel with flashbacks for more World War II stories before ultimately landing on the conspiracy genre as a unique take on the sequel that would contrast with the “war film” elements of The First Avenger.

Markus and McFeely had mostly free reign to tell the story they wanted, but Marvel Studios president Kevin Feige had two major beats he wanted included: the helicarriers at the end of the movie, and the fall of S.H.I.E.L.D. To that end, Markus and McFeely pulled from films like Three Days of the Condor, The Parallax View, and Marathon Man, forcing Steve Rogers to face an America he doesn’t recognize while in the belly of a shadowy governmental organization. The end result? Dismantling S.H.I.E.L.D. altogether and removing the Avengers’ safety net when Age of Ultron rolled around.

When it came time to hiring a director, Marvel Studios moved away from the big names of Phase One like Jon Favreau and Kenneth Branagh and narrowed the Winter Soldier pool to George Nolfi (The Adjustment Bureau), F. Gary Gray (The Italian Job), and Anthony and Joe Russo, with the latter directing team having helmed a couple of films (You, Me, and Dupree being their most notable) but having recently spent a lot of time directing television.

In April 2012, Gray took his name out of the running to instead direct Straight Outta Compton, and by June the Russo Brothers had the job. The Russos directed the pilot for Arrested Development and a number of episodes of that groundbreaking series, but it was actually their work on Community that put them on Marvel’s radar—specifically directing the action and Western spoof episodes “A Fistful of Paintballs” and “For a Few Paintballs More.” When they got a meeting with Marvel, they expressed their intense love of the comics and the Captain America character, and their mentor Steven Soderbergh even called up Marvel and put in a good word.

The decision proved fortuitous, as the Russos would not only direct The Winter Soldier but also Captain America: Civil War and the massive two-part Avengers: Infinity War and Avengers: Endgame. But we’ll get to those later.

Back to Captain America 2, Marvel confirmed the Russos and revealed the sequel’s title at San Diego Comic-Con 2012, causing the audience to erupt with applause when “Captain America: The Winter Soldier” graced the screens in Hall H. This signaled that the film would be an adaptation of the Ed Brubaker storyline The Winter Soldier, which brings Bucky Barnes (Sebastian Stan) back to go toe-to-toe with Steve Rogers as a brainwashed assassin.

The filmmaking team wanted to give Steve Rogers some other characters to play off of, and explored different iterations. At one point Jeremy Renner’s Hawkeye was in the film, and at another point he was in it in addition to Scarlett Johansson’s Black Widow, until eventually it was decided to simply pair Steve up with Widow and then add Falcon to the mix. For the latter role, Marvel hired Anthony Mackie, while the search then began for an unnamed female lead that would eventually be revealed to be Sharon Carter.

While Sharon Carter ultimately doesn’t have a major role in The Winter Soldier, nor in subsequent MCU movies, the possibility was there, and Marvel considered a number of actresses for the part. Emilia Clarke, Alison Brie, Imogen Poots, Teresa Palmer, and Jessica Brown Findlay all reportedly tested for the part, but it eventually went to Emily Van Camp who was hot off the ABC series Revenge.

For the part of villain Crossbones, who ended up being slightly more significant than Sharon Carter in the MCU, Marvel considered Josh Holloway (Lost) and Nikolaj Coster-Waldau before settling on Frank Grillo.

Samuel L. Jackson and Cobie Smulders reprised their roles as S.H.I.E.L.D. agents in a major way, but a huge casting surprise was saved for just before filming began, as Robert Redford joined the ensemble. Of course, in hindsight we learned that Redford was playing the surprise Big Bad, but at the time it was curious to see an actor of his caliber added to the mix as a high-level S.H.I.E.L.D. agent. This would not be the last time an extremely famous, award-winning actor joined the MCU.

Filming on Captain America: The Winter Soldier began on April 1, 2013 and set up shop in Cleveland, Ohio, which also served as a major filming location for Marvel’s The Avengers thanks to a generous tax break. And in contrast to the production of Thor: The Dark World, the entire process on The Winter Soldier ran incredibly smoothly. Which explains why Marvel kept rehiring the Russo Brothers again and again (and also why this installment of How the MCU Was Made is slightly boring).

Captain America: The Winter Soldier opened in theaters on April 4, 2014 to positive reviews and a stellar $95 million opening weekend. It would go on to gross $714.2 million worldwide, which was nearly twice the lifetime gross of The First Avenger. Indeed, Marvel’s Phase Two would be marked by significant box office gains thanks to the massive success of Marvel’s The Avengers, which served as an advertisement of sorts for fans to seek out and continue on with the adventures of the individual characters.

But before they could get to another sequel, Marvel embarked on its biggest gamble since perhaps the first Iron Man. A space-set movie in which two of the main characters are a sentient tree and a talking raccoon. Next week, we dig into the making of Guardians of the Galaxy.