The impressively long history of the comic superhero Captain America began in December 1940, a full year before the bombing of Pearl Harbor brought the United States into World War II. "As the ruthless war-mongers of Europe focus their eyes on a peace-loving America..the youth of our country heed the call to arm for defense," came the bold declaration on the first page of Captain America Comics. One of those young men was Steve Rogers, a skinny artist full of the patriotic fever to join the armed forces, but who was too sickly and unfit to join.
Luckily for Steve, the American government had been working on a Super-Soldier Serum as one of their tools to combat the Nazis and their allies. "Little does he realize," Professor Reinstein (or Erskine, as he is later renamed) mused minutes after injecting Steve with the Super-Soldier Serum, "That the serum coursing through his blood is rapidly building his body and brain tissues, until his stature and intelligence increase to an amazing degree!..It is working! There's power surging through those growing musclesmillions of cells forming at incredible speed!"
The professor's enthusiastic ramblings translate to mean that Steve Rogers was indeed the prime human specimen. He represented a human at peak physical condition, in strength, stamina, intelligence, senses, and speed. His power levels have fluctuated over the years, sometimes boasting the ability to run a mile in a minute, but traditionally, he has had more in common with a really fit Batman than Superman.
Unfortunately for Professor Reinstein, he did not live long enough to see the incredible feats his serum would inspire. Reflecting a trend that would be present in many of the 1940s Captain America Comics, Nazi spies were afoot and in an effort to steal the Super-Soldier Serum for their own and stop the United States from producing any more Captain Americas, Professor Reinstein was killed. But before he died, he christened Steve Rogers with his new name, explaining, "We shall call you Captain Americabecause like you, America shall gain the strength and the will to safeguard our shores."
As with most superheroes, Captain America needed a secret identity of sorts. Shipped off to Camp Lehigh, Steve posed as the bumbling and clueless Private Rogers when he wasn't donning his trademark costume star-spangled costume and matching shield. While at Lehigh, Rogers met James Buchanan "Bucky" Barnes, a mascot of the camp. In the original story, Bucky walked in on Steve changing out of his Captain America costume. This secreted Bucky's sidekick status because "From now on we must both share this secret togetherthat means you're my partner, Bucky!" Of course, those were the innocent days before both Marvel and DC comics started killing off sidekicks left and right, and no further explanation was needed for why Captain America would want a sidekick. In the years since, Marvel's changed the Bucky origin story several times, in an attempt to make the teenager fighting at Steve's side look more plausible. Bucky went from being the Camp mascot to being a trained operative w ho executes covert assassinations that normal soldiers and Captain America could not do. The reasons for Steve taking him on as a sidekick have changed from being Steve's idea to Bucky blackmailing him into taking him on in exchange for keeping Steve's secret identity a secret. Once Bucky became the trained agent of the military, it was retconned that he was "given" to Captain America by the United States government.
Regardless of the exact reason or circumstances for why Bucky Barnes was a part of Captain America's life, together Cap and Bucky, either solo or as part of the superhero team the Invaders, fought against the Nazi and Japanese threats. Two of their major enemies during this time included the Red Skull and Baron Zemo, both of whom would continue to reoccur as villains during Cap's later career.
As World War II came to a close, sales of all comics plummeted. Even Captain America Comics, which had sold approximately 1 million copies a month at its high point, began to suffer sales wise. After some drastic changes, such as wounding Bucky, giving the role of sidekick to Cap's girlfriend Betsy Ross, and revamping Cap into a communist hunter, the Captain America comic was cancelled in 1954.
But cancellation, like death, is short lived in comics. Ten years later, Steve Rogers and Captain America were brought back in Avengers #4. In this new version of continuity, it was revealed that Steve Rogers and the original Bucky were lost shortly after the end of World War II (the post-World War II appearances of Cap and Bucky would later be explained away as different Caps and Buckys entirely.) When trying to stop a plane programmed by Baron Zemo, Bucky was apparently killed and Cap fell to the icy waters below, where he remained in a block of ice until the Avengers found him.
Steve's first thoughts were of his fallen partner, and Bucky's death and the guilt that Steve had over it continued to be one of two major themes in the Captain America tales that followed.
The pain over Bucky's death didn't stop Steve from acquiring new partners, of course. After becoming a member of the Avengers, Steve quickly stepped into leadership and training of the younger members, a sampling of whom would grow to include Hawkeye, Iron Man, and the Young Avengers. Heavy emphasis was often placed on Cap's fighting skills and he was often given credit for being the best hand to hand fighter in the Marvel universe.
In addition to his Avengers adventures, Captain America became an active part of planetary peacekeeping force S.H.I.E.L.D. and picked up two new fighting partners. The first, Rick Jones, even wore a Bucky costume for a while. The second, Sam Wilson was written as Captain America's partner, and less like the sidekick that both Rick Jones and Bucky were.