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NOTE: This article is about the incarnation of the Winter Soldier from the Marvel Cinematic film series. The mainstream version can be found here: Winter Soldier.
(Captain America: This doesn't have to end in a fight, Buck.) It always ends in a fight.
~ Captain America and Bucky Barnes.
James Buchanan "Bucky" Barnes, later known as the Winter Soldier and White Wolf, is a major character in the Marvel Cinematic Universe. He serves as the tritagonist of Captain America: The First Avenger, as the titular secondary antagonist of Captain America: The Winter Soldier, and as the deuteragonist of Captain America: Civil War. He later returned as a minor character in both Ant-Man and Black Panther, and as one of the tritagonists of both Avengers: Infinity War and Avengers: Endgame.
Bucky Barnes was extremely loyal, devoted, trustworthy, headstrong, and patriotic, so he had a strong moral center. He was a good and close friend to Steve Rogers during their youth; he helped him when he got into fights and tried to cheer him up and look after him when Rogers' mother died. Best friends since childhood, they went through many trials and tribulations together. He was also protective of Rogers, as when he planned to enlist in the United States Army. Barnes tried to talk him out of it, as he knew he would die because of his physical condition and poor health.
Due to his advanced physiology, however, Barnes survived his apparent death, but was found by HYDRA instead. Trained as a living weapon, Barnes became a new man so to speak as his memories and identity were constantly being wiped until he was augmented into the perfect assassin, the Winter Soldier. As the Solider, he was brutal and ruthless with an utter lack of conscience, and followed remorselessly on HYDRA's any order. Even so, he still saved Steve Rogers from drowning after the Insight Helicarrier blew up. Although he states he did not know why he did such, it was due to Rogers reminding him of who he was, which he initially reacted with violence before finally accepting.
While he still holds a mostly serious demeanor, he is still shown to retain a sense of humor, as shown when he and Falcon both smiled with approval at Rogers' kiss with Sharon Carter and later as the two reminisced over earlier times in their friendship. His sense of humor can also be dry at times, as shown when he asked Wilson why he couldn't use his gadget on Spider-Man earlier to take him down.
Even though Barnes has regained his identity and former values, he has also developed a guilt-ridden conscience, and became deeply ashamed over his actions as the Winter Soldier. He previously stated that he has an absolute memory of every person he has killed, and knows that the fact he was brainwashed does not change the fact that he killed them. Fearing for his mental state and anyone around him (as Helmut Zemo was able to manipulate him with the Winter Soldier Program), Barnes ultimately decided that placing himself in cryogenic stasis until he can be cured of HYDRA's mental programming completely would be the best course of action.
Captain America: The First Avenger
Bucky is first seen in the film as a sergeant in the US Army. He sees Steve being beat up by a bully and comforts him after a brief confrontation. He takes Steve and two girls to a World of Tomorrow Exhibit and departs to be deployed. He is next seen where he is being held captive by HYDRA and stripped to a chair. Captain America rescues him, only to find himself meeting Johann Schmidt, better known as the Red Skull. Afterwards, Captain America recruits him as his second-in-command of the Howling Commandos team to square off against Red Skull's HYDRA henchmen and destroy every HYDRA base in the overseas area. He is last seen in this film when Captain America and his team are deployed to bring HYDRA scientist Arnim Zola into custody. When a HYDRA goon fires at Bucky with the Captain's shield, he instead is sent on the side of the train. Before Captain America could save Bucky, he falls to his apparent death into an icy cold riverside.
Captain America: The Winter Soldier
It turns out that Bucky survived his fall, but was found by HYDRA and brainwashed into an assassin operative of HYDRA as The Winter Soldier. He is first seen when Nick Fury was being chased by rogue policemen sent by Pierce to kill him. He shot a grenade at Fury's car and made it fly into the air. He then follows Fury to Captain America's apartment and severely wounds him. Captain America throws his shield at the Winter Soldier, but he reflects it and throws it back at Captain America.
The Black Widow reveals that she had a recent encounter with the Winter Soldier and unveils that he is a ghost to most of the intelligence society. He is next shown when he is sent to Alexander Pierce's home to receive his next assignment. Pierce tells him that his next targets were to be Captain America and the Black Widow, who were attempting to discover Pierce's plan to use the SHIELD Helicarriers and target over a million people. Afterwards, he attacks Rogers, Natasha Romanoff and Sam Wilson, who were driving while proceeding with their investigation of Jasper Sitwell and the revelation of HYDRA's plan. After he kills Sitwell, the Winter Soldier tries to fire a grenade at Rogers and Romanoff, but Rogers deflects it and it ends up destroying a bus. While engaging Black Widow, the Winter Soldier pursues her through the streets of Washington, DC before coming across Rogers. After a one-on-one duel, Rogers rips off his mask and discovers that the Winter Soldier is actually Bucky. Before he could raise his gun, Bucky was knocked to the ground by Wilson.
Back at the lair, the Winter Soldier starts to remember his past while trying to give Alexander Pierce a full report on his mission. Pierce then puts him into another brainwashing treatment making him forget everything from his past life, though this time, the brainwash effect not last long. During the climax, Winter Soldier fought Captain America, but the Helicarrier where they fought, along with everyone on board, crashes.
Eventually, the brainwash effect upon the Winter Soldier wore off. Regaining his senses, he rescues Captain America from drowning, before disappearing and takes Pierce with him. In a post-credits scene, the Winter Soldier visits the Captain America exhibit at the Smithsonian Institution to learn of his past, hints a sign of possible redemption; with his memory back and the brainwash effect wore off, he is likely less evil in the end and he likely wanted to meet his old friend.
Between Captain America: The Winter Soldier and Ant-Man
But beforehand, Bucky decided to returned to Ideal Federal Savings Bank, where he falsely informed two scientists present that Captain America was dead. As the scientists relaxed momentarily, Barnes attacked and attempted to kill them and began destroying much of the machinery which had been used to control and torture him for so many decades. However, as memories and images of past assassinations for HYDRA raced through his mind, Barnes relented and fled to try and get away from his violent history and learn the truth about his past once and for all.
In spite of his redemption by saving his old friend Steve, Bucky decided to go on the run from the government out of guilt for his crime when he was evil due to Pierce’s brainwashing. However, Sam and Steve managed to track him down in a remote location. At first, he decided to resist, but they anticipating this by trapping his cybernetic arm in a vice, making him defenseless and unable to fight. When realizing that Steve also comes along to hunt him, Bucky decided to accept his defeat. Steve then asks Bucky whether he knew who he was; Bucky replied that Steve's mother was Sarah Rogers. Rogers and Wilson discussed recruiting him, noting that they would not inform Tony Stark of Barnes' capture and that Wilson knew a guy who could assist them.
Captain America: Civil War
In Captain America: Civil War, Bucky returned as the tritagonist one again. Here, it's revealed that after his brainwash into a Winter Soldier by HYDRA, five other soldiers were also brainwashed in the same way into other Winter Soldiers and locked and frozen due to fear that they would rampage and start the riot. HYDRA also revealed to have arranged a fail-safe procedure in his brainwashing process in form of trigger words that would revert Barnes to his brainwashed self for a certain amount of time should he revert to his original good self and turn against them.
Eventually, Bucky decides that it is best for him to return to cryo-sleep until his identity can be fully restored and is frozen in Wakanda.
Bucky makes a cameo appearance in the film as he is put out of cryo-sleep following the death of Erik Killmonger. He is seen trying to recover outside of the Wakanda hospital with the aid of Shuri, Black Panther's younger sister.
Avengers: Infinity War
Bucky returns in the film, as he has been finally rid of his HYDRA brainwashing for good while awaiting the arrival of several more Avengers coming to Wakanda. Going by the name White Wolf, Bucky learns from the other Avengers that the alien warlord Thanos is plotting to collect all six Infinity Stones to wipe out half of the universe' populace. He also learned that Vision has the Mind Stone on his forehead and plans to have it removed so that Scarlet Witch can destroy it to foil Thanos' plot.
After Thanos collected five of the Infinity Stones, he assembles the Black Order and their army of Outriders to attack Wakanda. Along with the other Avengers and the Wakandan warriors, Bucky fought back against Thanos' forces in order to buy enough time for the Mind Stone to be removed and destroyed by Scarlet Witch. Unfortunately, an arriving Thanos used the Time Stone to reverse this, allowing himself to take the Mind Stone while killing Vision. Thanos then used the power of the Infinity Stones to wipe out half of the universe's populace, and Bucky ends up being disintegrated to his death along with several other Avengers, much to Steve's distraught.
Five years following the death wave, the surviving Avengers perfected a successful plot of travelling back in time to retrieve the Infinity Stones and used them to revive everyone who perished, including Bucky. However, the 2014 Thanos learns about this and travels to the present with his vast armies of the Black Order, Chitauri soldiers, Leviathans, and Sakaaran Mercenaries, intending to steal the Stones so that he can destroy the universe and rebuilt it in his own image. Fortunately, Bucky and the other revived heroes came to the rescue, allowing Iron Man to sacrifice himself by using the Stones to disintegrate Thanos and his forces for good.
Bucky would later attend Stark's funeral along with the other Avengers before witnessing Captain America returning the Stones back to their proper timelines. He is eventually surprised to see that Captain America has returned to the present as an elderly man passing on his sheild to Sam Wilson.
Powers and Skills
Super-Soldier Serum: As a super-soldier, he has all the physical abilities of Captain America, ranging from increased strength, speed, reflexes, stamina, durability, healing, senses, mental faculties and longevity.
Cybernetic Arm: His left arm is cybernetic, allowing him higher levels of superhuman strength.
Master Combatant: He is a highly skilled martial artist, being one of the best in the world. He is also a professional espionage operative, stealth tactician and sharpshooter.