John Walker, Marvel Comics' US Agent, is now a full-fledged member of the Marvel Cinematic Universe, and given the events of Disney Plus's now-completed The Falcon and the Winter Soldier, it looks like his MCU story isn't over.
Played by Wyatt Russell, John Walker was the United States government's choice to replace Steve Rogers as Captain America following Steve's 'retirement' at the end of Avengers: Endgame.
But Walker's tenure ended almost as soon as it began, with readers of Marvel Comics knowing a fall from grace as Cap was always where his story was headed.
For MCU fans unfamiliar with his story arc, here's a look back at the comic book history of Walker, how he (briefly) became Captain America and evolved into the current US Agent, and what the comics tell us about his MCU future.
Spoilers ahead for The Falcon and Winter Soldier.
Who is U.S. Agent?
In the comic books back in the '80s, Steve Rogers was undergoing a crisis of faith in his role as Captain America, something he struggled with previously that led to him briefly giving up his identity as Captain America to become Nomad a decade before. But this time was a little different – Cap was being asked to do things he wouldn't normally do, with his usually lax government oversight replaced by a tribunal who felt it was their duty to strictly order his activities.
Bristling at both the eyes over his shoulder and the tasks he was being asked to perform, which he felt were not becoming the mantle of Captain America, Rogers resigned, handing in his shield and costume, and taking up a black, white, and red ensemble that, while resembling his Captain America suit, was not directly tied to a patriotic theme. Steve began calling himself simply 'The Captain,' and set about his usual crime-fighting, Avenging routine.
But the Commission on Superhuman Activities, the government taskforce ordered to oversee Cap's duties, wasn't so keen on losing America's personal superhero, so they reached out to find a replacement willing to don Cap's shield and costume – and to follow their strict directives.
Enter John Walker – a Georgia-born soldier stationed at Fort Bragg who so idolizes his older brother, a war hero who died in Vietnam, he enlists the help of the villainous Power Broker to give him superpowers. At first entering superhuman wrestling leagues, Walker catches the eye of a publicist, who convinces him to try his hand at being a full-on superhero.
Taking up the name Super Patriot, Walker uses his newly imbued super-strength to begin following in the footsteps of Captain America, through the lens of his own right-wing politics. Walker's publicist begins orchestrating a series of high-profile fights against supposed pro-Steve Rogers activists – actually actors hired to make Walker look like a good choice to replace Rogers, something the then-Super Patriot is already gunning for before Steve's retirement.
The scheme works, and when Super Patriot makes a high-profile rescue just as Rogers quits, Walker is hired as the replacement Captain America. But things quickly go south – first, Walker is sent by a rogue agent to help hunt down political adversaries to the brutal regime of a South American dictator, which cause him to become disillusioned, then his violent methods as Captain America lead terrorists known as the Watchdogs to kill his parents after his secret identity is revealed on television.
When Walker's strict orders force him to miss their funeral, he becomes emotionally unstable and murders numerous members of the Watchdogs. As a result, he's captured by the fascist Flag-Smasher, but he's rescued by Steve Rogers, operating as the Captain.
Subsequently, Walker is manipulated by the Red Skull into confronting Rogers in Washington, DC – but the two heroes quickly realize what's happening, after Walker decimates Red Skull's henchmen, and team up to bring down the arch-villain. After this, Walker gives Steve back the Captain America shield and costume, and takes up Steve's black, white, and red 'Captain' uniform as US Agent, complete with a new, matching shield.
How does US Agent fit into the Marvel Universe?
Following taking the mantle of US Agent, Walker became a staple of the Marvel Universe throughout the '90s, serving on both the Avengers West Coast and the core Avengers team over the years – though he was also once tricked into turning on his teammates alongside his fellow 'replacement heroes' War Machine and Beta Ray Bill, who had filled in for Iron Man and Thor in previous years. Walker also served as an agent of SHIELD, a member of the Invaders, and even a member of Canadian team Omega Flight.
But tragedy struck when Walker was dismembered by the villain Nuke, using Odin's spear, while Nuke was part of the Thunderbolts - then a sort of private black ops team run by Norman Osborn. A few years later, while using a wheelchair and prosthetic arm, Walker became the warden of a new Thunderbolts program in which Luke Cage led a team of former villains trying to rehabilitate into heroes.
In the course of his time with the Thunderbolts, Walker wound up in an alternate reality where a scientist was able to regrow his lost limbs.
Walker will co-star in the upcoming United States of Captain America limited series, in which Steve Rogers, Sam Wilson, Bucky Barnes, and John Walker all team up for a road trip adventure celebrating the 80th anniversary of Captain America's 1941 debut.
How does US Agent fit into the Marvel Cinematic Universe?
As previously mentioned, John Walker's career as Captain America has already come and gone, but his MCU story isn't over.
In The Falcon and the Winter Soldier episode four, Walker ingested some of the Power Broker's Super Soldier Serum, bringing in a previously unused part of his comic book backstory in which the Power Broker gives him super strength.
Unfortunately, Walker's comic book history reared its ugly head in some other ways, with Walker violently beating one of the Flag-Smashers to death with his shield in full view of numerous civilians as well as Sam and Bucky – a plot point taken straight from comic books where Walker becomes increasingly violent in his duties as Captain America.
After a short fight with Sam and Bucky in the aftermath in episode five in which Sam eventually takes the still-bloody shield from him, Walker is brought back to the US, stripped of the mantle of Captain America, and discharged from the military.
Despite murdering a man while caught on camera, which turns into an international incident, he isn't arrested or charged with a crime; a somewhat dubious plot development that might be necessary if given what now seems like Walker's comic book story closely playing out in the MCU.
In the comics, Walker eventually receives treatment for the aspects of Power Broker's serum that exacerbate his anger and violent outbursts. And in the MCU, it seems the serum played a role in Walker's escalation, as Lemar Hoskins/Battlestar pointed out the power the serum gives to people seems to magnify a person's true personality.
But it's also Lemar's death at the hands of the Flag-Smashers that leads to Walker losing control.
The Falcon and the Winter Soldier explored the nature of Captain America and the legacy of Steve Rogers, and what it means to embody that role and carry the vaunted shield that comes with it. The differing ideology between Sam Wilson and John Walker came into stark relief, with Sam now fully embracing the shield and the mantle of Captain America.
But there appears to still be room for Walker in the MCU, although with some significant red flags and question marks.
Towards the end of episode six, Walker does something of a hero turn, helping save some innocents despite initially seeming single-mindedly focused on fighting Karli and the Flag-Smashers.
Wilson and Walker even share a respectful nod after the fighting is said and done, and Walker seems to silently indicate he's accepting of Sam as Cap. But questions about Walker's mental state and his allegiances remain.
Towards the end of the finale, Walker and his wife are again seen with Julia Louis-Dreyfus's mysterious new character Valentina Allegra de Fontaine.
"Things are about to get weird," de Fontaine ominously predicts, "so when they do, we're not going to need a Captain America, we're going to need a US Agent," officially re-introducing Walker in his long-time identity, with a new black version of his Cap costume that closely skews with his classic comic book costume.
His home workshop shield from the episode five mid-credits teaser is predictably destroyed during the finale's action scenes and a new one doesn't appear in his final appearance, but since his and de Fontaine's story (Walker appears like he'll be an 'agent' to whatever her schemes wind up being) will clearly continue, that will likely be addressed whenever and wherever he appears next.
His history is complicated, but John Walker does make Newsarama's list of the best Marvel Comics characters to yield Captain America's shield.