Baron Heinrich Zemo was one of the most brilliant scientists of all Nazi Germany, and joined the Nazi party early in it's existence. Zemo quickly became one of the Nazis' top scientists and the most wanted Axis agent. One of his first public activities occurred when Allied Sergeant Nick Fury invaded Zemo's castle to destroy Zemo's death ray. The defeat left him vilified throughout the world, and even in Germany, where Zemo took his wife and son, Helmut, into hiding. Zemo began wearing a cowl to disguise himself.
Zemo was working on his invention known as Adhesive X when the hero Captain America invaded his laboratories. In the course of destroying the only supply, the adhesive covered Zemo's cowled head, which became permanently affixed. As a result, Zemo became consumed with a violent, insane hatred for Captain America and mankind in general.
Zemo led many missions of sabotage and terror against the Allies, often clashing with Captain America. Late in the war, Captain America and his sidekick Bucky tried to stop one such plan, but failed. It was believed that Bucky died in an explosion but would return years later as the Winter Soldier. Captain America was thrown into icy waters which led him into a period of suspended animation. Soon after, Zemo left Germany, and his family, in the final days of the war, hiding away in a base he had constructed in the South American jungle. Over the following decades, Zemo constructed a device to use his death ray against entire cities. About the same time, Captain America re-appeared, joined by the superhuman team the Avengers. Zemo created his own team of super-villains, calling them the Masters Of Evil, in order to destroy the Avengers, but they failed. Zemo clashed with the Avengers several times after that, including an attempt to destroy them by transforming Simon Williams into Wonder Man so that he could infiltrate the Avengers' ranks.
Ultimately, Zemo's plans were never successful. In his final attack against Captain America, he kidnapped the Captain's sidekick, Rick Jones, and brought him to his South American lair. Captain America rescued Jones, and when fleeing Zemo, the glare from Captain America's shield reflected into Zemo's eyes. Temporarily blinded, Zemo fired his death ray wildly, causing an avalanche that killed him.