Rogers was assigned to serve as an who served both as a counter-intelligence agent and a symbolic US hero to counter Nazi Germany's propaganda successes head by the Red Skull (Johann Shmidt). Wearing a costume based on his own design modeled after the American flag, Steve was given a triangular bulletproof shield, a personal sidearm and the codename Captain America, the Sentinel of Liberty. He was also provided a cover identity as a clumsy infantry private at Camp Lehigh in Virginia. His first opponents included the Red Skull himself and Nazi attempts to duplicate Erskine’s serum with their own super soldiers. During a mission to the African nation of Wakanda, “Cap” befriended the nation’s ruler T’Chaka and obtained a sample of the rare metal Vibranium. Subsequent experiments with this metal by Howard Stark produced a uniquely indestructible Vibranium-steel alloy disc, which proved impossible to duplicate. The disc was given to Cap as his new shield.
Barely out of his teens himself, Rogers made friends with the army’s camp mascot, teenager James Buchanan "Bucky" Barnes. Barnes accidentally learned of Rogers' dual identity and offered to keep the secret if he could become Captain America's sidekick. Rogers agreed, and trained Barnes. Throughout 1941, Cap and Bucky shared many adventures stateside and throughout the world. When the US entered World War II, Cap and Bucky teamed with the android Human Torch, his mutant sidekick Toro, and Namor the ocean-dwelling Sub-Mariner as the Allied force the Invaders.In the closing days of World War II in early 1945, Cap broke through Nazi troops for his final wartime confrontation with the Red Skull, who was seemingly slain by bombing debris (but lived on in suspended animation). Days later, Cap and Bucky arrived in England too late to prevent brilliant Nazi scientist Baron Zemo from obtaining and launching an experimental drone plane armed explosive device on it. Rogers and Barnes reached the plane, but when Bucky tried to defuse the bomb, it exploded in mid-air. Rogers was hurled into the freezing waters of the North Atlantic. The US government presumed both were dead. However, Bucky was secretly retrieved by Soviet operatives, while Cap was recovered by Nazi agent Lyle Dekker, who hoped to exchange bodies with him. Cap escaped Dekker’s base by air, but was shot down and fell back into the ocean. Due to the Super-Soldier serum Captain America survived, entering a state of suspended animation and eventually freezing in solid ice.