War Machine (Don Cheadle) suits up for action when the Iron Man technology invented by the late Tony Stark (Robert Downey Jr.) falls into the wrong hands in Armor Wars, one of the many Marvel Studios series in the works for Disney+. In the classic Marvel Comics story, Tony Stark wages all-out war on a gauntlet of armored villains — including Firepower, Stingray, the Crimson Dynamo, and the Titanium Man — who are powered by stolen Stark technology sold by industrialist Justin Hammer, Stark's chief rival.
In 2010's Iron Man 2, Hammer Industries CEO Justin Hammer (Sam Rockwell) attempts to replicate Stark's Arc Reactor tech after the genius playboy goes public with his short-lived secret identity in Iron Man. When the U.S. Air Force recruits the military contractor to upgrade and weaponize Stark's confiscated Mark II armor, Hammer creates the tank-like Variable Threat Response Battle Suit — better known as the War Machine armor piloted by Rhodes.
Stark and Rhodes team up to take out an army of rogue Hammer drones reprogrammed by Russian physicist Ivan Vanko (Mickey Rourke), who betrays his super-rich benefactor after Hammer recruits him to recreate Stark's Arc Reactor. Following the attack on the Stark Expo, Hammer is arrested by S.H.I.E.L.D. super-spy Natasha Romanoff (Scarlett Johansson).
Hammer returns in the One-Shot All Hail the King, taking place after the events of 2013's Iron Man 3, where he's among the inmates of the high-security Seagate Penitentiary housing the fake-Mandarin Trevor Slattery (Ben Kingsley).
By the time of Stark's self-sacrifice in Avengers: Endgame, set in 2023 after a five-year time jump, more than 13 years have passed since the start of Hammer's imprisonment — making it a possibility that he's a free man by the time of Armor Wars.
When a fan asked Marvel chief Kevin Feige about bringing back "forgotten characters" like Hammer during a Reddit Q&A in 2019, Feige replied: "I'm not sure I'd call them forgotten characters but I love bringing back characters people think they've seen the last of. For example, General Ross and Harley [Keener, from Iron Man 3]."
Asked about reprising the Justin Hammer role during his own Reddit Q&A last year, Rockwell answered he "would be happy to do it" and quipped that he's "just waiting on the Avengers to give me a call."