Tony Stark and Steve Rogers stand together in the open field of Clint Barton's family farm, talking shop and chopping wood. The two men disagree on how to best move forward in their battle against mechanical monster Ultron, and the argument eventually devolves into a debate about the future of the Avengers — an argument so contentious that Rogers actually rips a log apart with his bare hands.
It's a memorable moment not just in Avengers: Age of Ultron, but for the Marvel brand at large, as this was the starting point for what eventually became Captain America: Civil War. When Marvel's Kevin Feige confirmed the official slate of Phase Three movies at a Los Angeles event in 2014, he announced Civil War by playing the aforementioned scene for fans, giving a sense of the growing divide between two of the most important heroes in the Marvel Cinematic Universe.
For his part, Robert Downey Jr. didn't fully appreciate the significance of the philosophical farm fight right away. "It's funny," he says on the set of Civil War. "I never know when seeds are being laid. Sometimes, I'm just like, 'Wow, that's a pretty cool scene... are we laying seeds here?'"
At the time, Downey was too busy trying to wrap his head around Stark's next scene, involving Nick Fury and a John Deere tractor, to even consider what Steve splitting the log in two would represent for the future. Now, Downey knows all too well what's next: Iron Man and Captain America on opposite sides of the battlefield, exchanging repulsor ray blasts and Vibranium shield throws when words and wood can no longer solve the problem.
The exact reason for their break-up remains under wraps, but the movie version of Civil War will focus on the question of superhero oversight, with Tony advocating for more government regulation — a far cry from the cavalier renegade who publicly unmasked himself as a superhero in the very first Iron Man.
Downey rationalizes Tony's new position as a function of his age, seeing and experiencing more at this point in the Marvel Universe than where he was at the start.
"I think what's interesting is it's not so much that he's looking for more control," he says, "but that he's saying that as a group of individuals, we all require a little bit more supervision than we might imagine. That, for me, was just a really straight line."
Despite his best intentions, Tony's line is on a direct collision course with Cap's, leading to what Civil War co-director Joe Russo describes as a "very, very complex and dark arc" for the traditionally lighthearted Stark.
"I think you're going to see a side of Tony Stark you haven't seen in any of the films, and he's just crushing it," he says. "The Iron Man films sometimes have a lighter quality to them. This movie is pulling that center of gravity more toward the Winter Soldier intensity."
Indeed, the Winter Soldier himself is bound to draw much of that intensity out of Tony Stark. While Rogers fights tooth and nail to protect his old friend Bucky Barnes, Stark sees the brainwashed assassin without that same sentimentality — but the stakes are potentially even more personal. Fans have theorized that Bucky was responsible for the death of Tony's father, a theory co-writers Christopher Markus and Stephen McFeely won't confirm, at least not outright.
"It's implied that Hydra killed Howard Stark," says McFeely. "I think that's all we know for sure, is that they did that — and Bucky killed a lot of people."
Stark's not alone in his quest to stop Cap and Bucky. He's joined by his most tried and true friend, James "Rhodey" Rhodes, who earned a spot as an Avenger at the end of Age of Ultron. Also in Tony's corner: Vision, the artificial life-form born out of Stark's own genius.
"It was an immaculate conception," Downey jokes. "Tony wasn't setting out to have a baby with JARVIS. It just kind of happened that way!"
Tony has other allies as well, if not quite as sturdy as Vision and Rhodey: Scarlett Johansson's Black Widow, first introduced in Iron Man 2, will side with Tony, at least for some of the film. But her closeness with Steve, best seen in Captain America: The Winter Soldier, will pose problems for the spy.
"She's not trained to take sides. She's trained to be a duplicitous double-agent and have her loyalties for sale," says Markus. "It's almost tougher for her than anybody to go, 'This is my side, and I'm sticking to it."
Then there's T'Challa, the Wakanda prince better known as Black Panther. Chadwick Boseman makes his Marvel debut in Civil War ahead of his solo movie in 2018, and while he's Team Tony — at least during one major battle between the two sides — he's not necessarily steadfast in his support.
"He sees both sides of the coin," says Boseman. "It's necessary to protect your country. He understands that, because that's what he has to do. But there's a way to do it that is the best way. If it was The Art of War, it would be: 'How can you inflict less pain? How can less people die and still win the war?' He's a tactician. He's a strategist. He appreciates that thought process."
No matter where Tony and his allies ultimately land at the end of the film, the directors and writers expect and hope fans will find themselves just as divided as the heroes.
"What's fun about this is that depending on what side you're on, the [antagonists] are different," says Markus. "It depends on how passionate you are about your side. This isn't a traditional 'I want to rule the world' bad guy. Things are grayer. There are some strings being pulled and interesting things going on that are of a debatable moral quality."
"We want people walking out of this movie going, 'Tony's right,' and the other half of people going, 'Steve's right,'" adds McFeely. "It would be a dream if we got a 49-51 split."
Captain America: Civil War hits theaters on May 6, 2016.