It’s Avengers 2.5.

That was the worry as Captain America: Civil War went into production with a whole cavalcade of heroes involved, and that’s been one of the comments that you’ll see pop up in the wake of the film’s release - “It’s not really Cap’s movie, it’s really an Avengers movie.”

And you can see why. Almost all of The Avengers are in the film, and what’s more, they all have something to do and they all have story arcs (however small) of their own. Just in terms of the optics, Civil War looks a lot like an Avengers movie. The most memorable moments are moments that involve other Avengers. Hell, all the advertising has included all of The Avengers facing off against each other.

But don’t let the optics confuse you. Don’t let the fact that the Russo Bros (and screenwriters Christopher Markus and Stephen McFeely) have a real affinity for an ensemble fool you. Take away Giant-Man and Spider-Man, remove The Vision and Scarlet Witch, sideline Falcon and Black Widow, and you’ll see that you still have the same story, and that story is all about Steve Rogers and Bucky Barnes… and Tony Stark.

You have to recognize something right off the bat: Captain America is like Batman in that it can be fun to break him down and send him off alone, but he actually works best with a support system. Batman is the dad of the Batman Family while Cap is the leader of whatever squad he happens to be with at the time. In fact it’s his leadership skills - and his ability to motivate men and women in the toughest of times - that might be Steve Rogers’ true superpower. So as we saw in The First Avenger and in The Winter Soldier, you’re going to want to have Captain America at the center of an ensemble because what he does best is lead. In fact he doesn’t really become “Captain America” until after he busts Bucky (and the Howling Commandos) out of Hydra prison in The First Avenger.

That prison break, by the way, is the earliest foreshock of Civil War. Those who complain that Steve Rogers, a consummate New Deal Democrat, has suddenly become a selfish Libertarian who believes that his own hands are the safest maybe weren’t paying attention in the first film, where Steve disobeys direct orders to sneak behind enemy lines and save his best friend. And while he comes home with plenty of Allied soldiers in his wake, that mission was all about one man: saving Private Barnes.

From the beginning Steve was willing to go the distance (“until the end of the line”) for his best friend, so it should come as no shock that he’s doing it again in Civil War. At first Steve goes after Bucky not to save Bucky’s life but his soul - Steve knows that Bucky will kill anyone else who comes after him, and he doesn’t want to add any more bodies to his best friend’s debt - but eventually he decides that he has to clear his name, that Bucky is in fact innocent. And that’s where the Civil War (or really, civil disagreement) begins.

Take The Winter Soldier out of the movie. Remove the relationship between Steve and Bucky. What happens in the film? Steve refuses to sign the Sokovia Accords and… that’s it. I would guess that he can’t stay inactive, but I bet that he would just operate under the radar, being more tactical and focusing more on espionage. He would operate in a way that didn’t put him in direct conflict with Tony Stark, and if it did, there would be no emotional stakes high enough for Steve to escalate the conflict to violence. That scene on the tarmac, where Steve grits his teeth and decides to battle it out with his friends, never happens. There’s just no reason strong enough for him to risk his current friendships. If Zemo still bombs the signing of the Accords Steve probably feels that Tony's team is more than capable of dealing with it. There are no personal stakes for him.

The entire movie flows from the decisions made by three characters: Steve Rogers, Tony Stark and Helmut Zemo. Zemo, the mysterious villain pulling the strings, puts events into motion but everything that happens between the explosion in Vienna and the final fight in the missile silo comes from the decisions made by Tony and Steve, making them the central characters in the film.

So if Tony is a central character isn’t this a de facto Avengers story? Not quite, and that’s because Tony isn’t proactive in the story. He’s consistently chasing after Steve, which makes Steve the driver of the story. Again, without Steve making these decisions there is no movie at all. In fact it’s when Tony does get proactive - when he very much goes after the Winter Soldier - that his true role in the movie becomes clear as he moves from foil to antagonist. Yes, Zemo is the villain, but Tony is the antagonist (technically Steve could be seen as the antagonist if this were Tony’s movie, but again since Tony isn’t driving the story…).

The airport fight might seem like the climax of the film - it’s certainly what we’re all going to remember about this movie - but it’s a feint. That airport fight could be almost completely removed without harming the actual story, the story that sees Steve doing whatever he can to clear the name of his best friend, even if it means coming into direct conflict with his new friends. It’s the optics at play - because the airport fight looms so large, and because it has all of The Avengers in it, you feel like you’re watching an Avengers movie. But as awesome as that fight is, the real meat of the conflict doesn’t come until the missile silo (the airport fight is a huge feint on a lot of levels; you feel like you’re seeing the expected outcome of a story called “Civil War,” you see that the heroes don’t really want to hurt each other, which makes the brutality of the final fight hit harder, and you get set up for what looks like an ending where the heroes come together to stop the real baddie).

Beyond being the center of, and driver of, the plot, the Steve/Bucky relationship also reflects most of the film’s thematic concerns. Steve doesn’t trust government oversight partially because in the last film he learned that SHIELD was a front for Hydra but also because his best friend was once sent out on assassination missions with full governmental oversight. The Winter Soldier program is the embodiment of all of Cap’s fears, a program that keeps the super soldiers on ice until they are used only as weapons. This harkens back all the way to the beginning, to the idea that the difference between Captain America and The Red Skull was not the serum or the process but the men themselves. One man becomes twisted and evil, one man becomes a great hero. It's not the abilities, it's the character of the man in charge of the abilities, and Steve trusts his own character more than that of a shifting group of UN bureaucrats.

That feeds into the larger theme of responsibility. In this film Tony Stark is looking to get rid of it - Steve accuses him of siding with the Accords as a way of shifting the blame to someone else. Responsibility has been a question that Steve Rogers has mulled from the very first film, from before he was a super soldier. A scrawny 4F reject, he felt he had the responsibility to fight in the war, right up front, not back at home. When a grenade is tossed onto the parade grounds during his basic training he takes immediate personal responsibility and throws himself atop it. When his best friend is captured he takes it upon himself to rescue him. And at the end of the movie, when The Red Skull’s flying wing is headed to New York, he takes the ultimate responsibility and crashes it with himself aboard.

Add to that his decisions in The Winter Soldier - shutting down SHIELD, for instance - and you see just how central Steve Rogers is to Civil War. This is a movie that is paying off all of these moments, and only one character in the Marvel Cinematic Universe could have made these choices in this way. Again, without Steve Rogers at the center of the film, driving all the decisions, there is no film.

Steve and Bucky’s relationship reflects responsibility in other ways. There is a metaphor for mental illness underlying the entirety of The Winter Soldier’s storyline - the idea that it is Bucky Barnes committing these murders (and remembering them all) while at the same time not being in control of his own actions, that something inside his mind is driving him. What is his responsibility for his crimes? For Tony Stark the answer, in the end, is black and white - Bucky has to pay with his life, a very extreme law and order sentiment based on extreme emotion. Punishment is the only option. For Steve Rogers the answer is rehabilitation. Bucky can be healed, he can atone for his actions. The question of punishment versus rehabilitation is, in many ways, a refraction of the main theme of where responsibility lies - in the individual or in the government?

And again, these themes are only possible with the Steve and Bucky relationship, and with the decisions that Steve makes over the course of the film. And it’s the strength of that central relationship - Crossbones simply mentioning Bucky’s name puts Steve off his game (hey, just like what happens with future lovers The Vision and Scarlet Witch… hmmm) - that sets all the events of this movie into motion. Zemo’s plan works, but it had to be predicated on one thing: that Bucky is the most important person in Steve Rogers’ life. That, when push comes to shove, Steve would choose Bucky over literally everything else in his life, including being an Avenger, his friendship with Tony Stark and even being a free man.

What makes Civil War such a fun movie is the way it brings in so many of the Marvel characters to face off, but what makes Civil War a good movie - and essentially, undeniably a Captain America movie - is the emotional core that supports the skirmish. It isn’t the Sokovia Accords that start the Civil War - it’s Steve’s decision to stand by Bucky, no matter what. Until the end of the line.