You may know Bucky Barnes as the Winter Soldier thanks to his trademark prosthetic arm. The arm has operated as a lethal weapon on several occasions, both when he worked as an assassin for Hydra and during his time with the Avengers.
However, when you watch Captain America: The First Avenger, you may notice Bucky has two real arms. So you might be wondering how Bucky lost his arm in the first place.
Bucky lost his arm during a mission to help Steve Rogers apprehend Dr. Arnim Zola. Having apparently fallen to his death, Bucky actually survived his fall, though he lost his arm in the process. He would have it replaced with a titanium prosthetic.
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How Did Bucky Lose His Real Arm in the MCU?
Bucky Barnes made his first appearance in Captain America: The First Avenger. During the film, he was initially presumed dead after he went missing in 1943.
Steve Rogers (Captain America) did not believe Bucky was dead and went on a mission to locate and rescue his longtime friend. He found Barnes and a group of prisoners at a Hydra compound before recruiting them to attack other Hydra bases.
In 1945, Rogers and Barnes infiltrated a train to subdue Dr. Arnim Zola. During the ensuing fight, Bucky fell from the train and to his apparent death. While he survived, Bucky lost his arm in the fall.
After he lost his real arm, Hydra again captured Barnes and replaced it with a titanium prosthetic. This arm, however, was one of many methods Hydra used to brainwash Barnes and to transform him into their assassin.
Scientists from a Soviet-based Hydra location created the arm. Initially, we believed Bucky used this same arm until 2016, but an episode of The Falcon and the Winter Soldier implied Bucky may have lost his first titanium arm before then.
In 1951, U.S. supersoldier Isaiah Bradley fought Bucky in Goyang. During the fight, Bradley claimed he took half of Bucky’s arm. However, Bradley also claimed the Winter Soldier “grew it back.”
Whether Bucky literally grew the arm back, or if he had it replaced at Hydra, we may never know. But Bradley’s story tells us that Bucky may have gotten a replacement for the titanium arm before Stark ripped it from him for good in 2016.
How Did Bucky Lose His Titanium Arm in the MCU?
In Captain America: Civil War, the Avengers found themselves on opposite ends of the Sokovia Accords. Tony Stark (Iron Man) led one group, who wished for government oversight that the Accords would bring.
Steve Rogers and those siding with him were against the Accords, stating his judgment superseded that of a United Nations (UN) panel. Tensions grew between Rogers and Stark. They climaxed when Stark discovered that Bucky Barnes had killed his parents.
Stark attacked Barnes, and Rogers interfered on his friend’s behalf. During the fight, Barnes tried to disable Stark’s Arc Reactor, but an ensuing unibeam from Stark destroyed the titanium arm.
Following the arm’s destruction, Barnes did not have the arm repaired or replaced, instead opting to have what remained of it removed.
Enter the Vibranium Arm
Following the loss of his titanium arm, Bucky lived in Wakanda. But when T’Challa (Black Panther) received word that Thanos’ army planned to invade the nation, he gifted Bucky a vibranium arm.
Bucky’s initial time with the vibranium arm didn’t last, as he was a victim of Thanos’ Blip (also called the Snap). When he and all the life that disintegrated returned in the Hulk’s Blip, Bucky retained his vibranium arm for the Battle of Earth during the climax of Avengers: Endgame.
Following Endgame, Bucky initially refused to expose his vibranium arm. But as time passed, he became more comfortable exposing the arm and only had it removed briefly when Ayo detached and revealed a locksafe within it.
How Did Bucky Lose His Arm in Guardians of the Galaxy Holiday Special?
The arm eventually ended up in Nebula’s hands, revealed during The Guardians of the Galaxy Holiday Special. In the 42 minute flick, Nebula gifted the arm to Rocket, who immediately recognized it as Bucky’s arm.
This left fans perplexed as to how Nebula ended up with the arm. James Gunn, who directed the film, stated that Nebula, “couldn’t help tearing the arm off because she was just feeling so Christmasy.”
We know that Nebula tore the arm off of Bucky sometime before December 2025, when the Guardians of the Galaxy Holiday Special took place. This also occurred after Sam Wilson delivered his Captain America speech.
As you may have guessed, Rocket was beside himself with glee upon getting the arm. We knew he wanted Bucky’s vibranium arm since Infinity War.
During the Battle of Wakanda, Rocket asked how much Bucky wanted for the arm. Bucky gave no answer and walked away. Afterward, Rocket vowed to get Bucky’s arm.
How Did Bucky Lose His Arm in the Comics?
In the comics, Bucky lost his arm thanks to an explosion after failing to defuse a bomb that Baron Zemo planted on a drone plane. A group of Soviets led by General Vasily Karpov found Bucky and they sent him to Department X.
While at Department X, Bucky received a bionic arm. As in the Marvel Cinematic Universe (MCU), Bucky also became the Winter Soldier in the comics. During his time as an assassin in the comics, the scientists at Department X regularly updated the technology in his bionic arm.
More On Bucky’s Bionic Arm
With each upgrade, Bucky’s bionic arm gained new ways to function. The actual technology itself remains a mystery. But we know that its composition was similar to vibranium thanks to its ability to withstand the Black Panther’s vibranium claws.
Bucky’s bionic arm could still function even if it got detached. This differed from the MCU, when Tony Stark rendered the arm useless when he destroyed it during Civil War.
Conclusion
Bucky initially lost his arm after he fell off a train to his apparent death in Captain America: The First Avenger. He had a titanium prosthetic attached to replace it, and for over seven decades working as an assassin, he kept that same arm.
However, Tony Stark destroyed Bucky’s arms in Captain America: Civil War. During a heated fight, Stark unleashed a unibeam, rendering the arm unusable. After two years, T’Challa gave Bucky a vibranium arm, which he had until Nebula ripped it from him in 2025.
Sion Fawkes has been covering Star Wars since January 2022, expanding his expertise in Star Wars Canon, Legends, and MCU. When not writing, you can find Sion in the gym or running trails. He also likes watching sports and listening to audiobooks.