When Captain America was introduced in the 1940s, his primary antagonist was the Nazi party and Adolf Hitler. However, he also fought other enemies in the Nazi party, like the deadly Red Skull, who eventually became his arch-nemesis. In the Marvel Cinematic Universe, Cap's history was slightly altered as he took on Nazis and an offshoot division known as Hydra. Hydra was a deep science division of the Nazi party that focused on harnessing the power of the gods for world domination, led by none other than Johann Schmidt, aka the Red Skull.
Source：https://www.cbr.com/red-skull-mcu-night-of-the-long-knives/
