Bucky Barnes was born on March 10, 1920, the first child of four to Irish Jewish immigrants. After meeting Steve Rogers as a child, he was an extremely loyal and devoted friend. While his devotion to Steve would eventually turn into a love that he kept secret, his protectiveness would never change. Bucky did everything he could to keep Steve safe and happy before he shipped off to war, including running his head into a brick wall multiple times while trying to talk Steve out of trying to enlist (again and again and again.)
Bucky was a Sergeant in the 107th Infantry Regiment of the US Army when he was shipped off to fight in WWII in 1943. While his unit was fighting on the front lines in Italy, they were attacked by a battalion of HYDRA soldiers. The men left alive, Bucky included, were taken prisoner and sent to work in a weapon production factory in Austria. During his imprisonment, Bucky was regularly beaten by guards, and when he fell too ill to work, was sent to Arnim Zola's laboratory to undergo experiments involving Zola's own version of the supersoldier serum.
It was during this time that Steve 'What Are Good Choices?' Rogers stormed the facility as Captain America, freeing prisoners and rescuing Bucky. In the mayhem, Zola and Johann Schmidt (who reveals himself to be Red Skull) escape. Though offered an honorary discharge and an opportunity to return home, Bucky chose to stay in the war effort and fight alongside Steve and the rest of the men that would become the Howling Commandos. Over the next two years, the team would work to dismantle HYDRA throughout Europe.
In 1945, on a mission to infiltrate a HYDRA train to take Zola prisoner, Steve and Bucky fall into a trap set by the HYDRA scientist. Though they are able to overcome the ambush, Bucky fell from the train into the frozen Danube River hundreds of feet below. Though his body was never found, he was presumed dead.
However, due to being experimented on by HYDRA, Bucky was able to survive the fall, though his left arm was ripped off on impact with the ground. His nearly lifeless body was later discovered by a Soviet soldier; he was subsequently handed over to HYDRA's Soviet wing. He was kept prisoner for many years until Zola was released from SSR custody, when he became Zola's lab rat again.
In the care of new HYDRA, working within S.H.I.E.L.D., Bucky underwent further experimentation as the first subject of the Winter Solder Program. It was during this time that the remnants of his left arm were removed and replaced with a cybernetic one, with extensions reaching into his left shoulder and down his spine to ensure the rest of his body is strong enough to support it. Bucky was also subjected to multiple mind control methods meant to keep him under their command. Over time, he lost all memories of his previous life.
With his body at the peak of physical perfection and his arm at the highest level of weaponized technology, HYDRA put the Winter Soldier to use as a deadly weapon. After every mission, HYDRA would wipe his mind to make sure he remained memory-free and emotionless, before freezing him in a cryostasis chamber to prevent any mental or physical deterioration. He was used to carry out many assassinations, including those of politicians and scientists. Stories and reports, spanning decades made him a legend and ghost story in the intelligence community. The Solder was also thawed and used as a training asset in the Red Room. At some point, he and Natasha Romanova started a romance that was quickly ended by HYDRA. Both were brainwashed to forget the other, and the Solder was put back into cryostasis.
In 1991, the Soldier was thawed and sent to America to kill Howard and Maria Stark in a staged car accident, and retrieve the Super Soldier Serum in Stark's car. In an effort to expand the Winter Soldier Program, HYDRA's top kill team was injected with the serum. Their enhanced physical attributes were even greater than the Soldier's, but were deemed too dangerous and unpredictable to be deployed. The five new Winter Solders were put in cryostasis chambers of their own, never to be unfrozen until a way to control them is found.
Barnes continues to be used as the only active Winter Soldier by HYDRA.
Hand to Hand Combat - Originally, Bucky was a three time YMCA welterweight boxing champion. Later, as the Winter Soldier, he received vast training from HYDRA, leaving him an extremely skilled and formidable martial artist and hand-to-hand combatant, excelling at improvisation and weapons handling.
Knife to Meet You - The Soldier excels in fighting with knives, with an emphasis in Kali knife fighting. In close quarters combat, the Soldier prefers to switch to his combat knife.
Expert Marksman - Bucky acted as a sniper during his time with the Howling Commandos, showing high proficiency and precision with firearms. He became even deadlier as the Soldier, able to make long range shots without the use of a rifle.
A+ Assassin - Even though the Soldier has been credited with over two dozen of HYDRA's most crucial assassinations in the last 50 years, most of the intelligence community does not believe he exists.
Multilingualism - The Soldier speaks his native English, as well as fluent Russian and German.