First Appearance: Captain America Comics #1 (March 1941).
Golden Age Appearances: Captain America Comics #1-66, All-Winners Comics #19, 21, Young Allies #1-20.
Modern Appearances: Captain America '98, Avengers #4, 15, 56, Avengers Annual #16, She-Hulk v2 #53, Tales of Suspense #63, 65, 66, Fantastic Four #405, Thor Corps #2.
Dates Active: 1941-1945.
James Buchanan Barnes was a ward of the state assigned to Camp Lehigh, the same camp in which Steve Rogers lived. Barnes accidentally discovered that Rogers was actually Captain America (I), and after undergoing intensive training became his costumed sidekick Bucky. During the Golden Age Bucky worked with Captain America in a variety of adventures, also helping to form the team the Young Allies. In 1948 Bucky was shown being wounded in action and replaced by Captain America's new sidekick, Golden Girl (I). He returned briefly in the 1950s when Captain America reappeared, but disappeared when Captain America did, and was not seen again.
Then, in the Silver Age, it was revealed that Bucky died in action, and as the years went by his history was added to, so that the current continuity for Bucky is this: he served with Cap in the Invaders, formed his own team of teenaged heroes the Kid Commandos, and was instrumental in bringing together the Liberty Legion. Towards the end of the war, in the spring of 1945, Bucky and Captain America went after Baron Zemo. Bucky was killed while trying to defuse a drone plane.
Bucky had no superpowers but was very athletic and a good fighter.