In 1945, in an attempt to capture HYDRA scientist Arnim Zola, Barnes was attacked and promptly plummeted off the side of a HYDRA train. He was then presumed to be deceased, though unbeknownst to his teammates Barnes had actually survived, due to the experiments performed on him by Zola while he was briefly captured as a POW, albeit with the loss of his left arm. Brainwashed and armed with a new cybernetic limb, Barnes ultimately became an enhanced HYDRA operative known as the Winter Soldier. Over the next several decades, he would eliminate anyone who posed a threat to HYDRA, including his former ally, Howard Stark. Between missions, Barnes would be put into a cryogenic stasis to preserve his longevity. Over half a century later, when he was ordered by HYDRA leader Alexander Pierce to assassinate S.H.I.E.L.D. Director Nick Fury, the Winter Soldier was confronted by his old friend, Steve Rogers, triggering him to begin remembering his prior life.
In the aftermath of the Battle at the Triskelion, the Winter Soldier went on the run from HYDRA on a self-imposed mission to remember his past and end his violent history. However, during this time Barnes was accused of being the perpetrator behind the Attack on the Jedi Temple, which claimed the lives of many. Barnes was saved by Captain America, sparking the Galatic Civil War as he also became a target for Senator June Finch and Iron Man. On the run from the ally forces, Captain America and Sam Wilson(Falcon) uncover the truth about the attack. With no support from the government, the fugitives build a small team tasked with taking down the Axis scheme. This squad consisted of Captain America, Falcon, Bucky Barnes, Batman, Bail Organa, Jack Sparrow, Indiana Jones, Deadpool, and Nightwing(who later defected).