James Buchanan "Bucky" Barnes, better known as the Winter Soldier, is a Marvel Comics character and former sidekick to Captain America. Bucky first appeared in the comic book "Captain America" #1 in 1941 as a teenager who became the sidekick of Captain America during World War II. In the comics, Bucky was believed to have died during the war but was later revealed to have been brainwashed by the Soviet Union and turned into a deadly assassin known as the Winter Soldier.
As the Winter Soldier, Bucky is a skilled fighter, proficient in hand-to-hand combat, marksmanship, and the use of various weapons. He also has a bionic arm that grants him superhuman strength and durability. After being freed from his brainwashing, Bucky has struggled to come to terms with his past actions as the Winter Soldier and has worked to redeem himself by becoming a hero in his own right.
Bucky has been a member of several superhero teams, including the Avengers and the Thunderbolts, and has also served as the Captain America when Steve Rogers was unable to continue in the role. In the Marvel Cinematic Universe, Bucky is portrayed by actor Sebastian Stan and has appeared in several films, including "Captain America: The Winter Soldier," "Captain America: Civil War," and "Avengers: Infinity War."