Jack Kirby was famous for being as tough as his characters. For instance, when a gangster was shaking down Kirby's boss, Will Eisner, to take his towel service, Kirby charged in to throw the gangster out. When Kirby created Captain America with Joe Simon, Nazi sympathizers once gathered in the lobby of the office building where the pair worked to threaten them. However, when upon hearing that Kirby was heading down with his sleeves rolled up to physically confront them himself, they fled before he arrived.
Peanut_Champion t1_jaeoair wrote
Reply to TIL Captain America co-creator Jack Kirby was drafted into the U.S. Army during WWII, landing at Omaha Beach in Normandy. When a lieutenant found out he was a comics artist, he made Kirby a scout who would advance into towns and draw reconnaissance maps and pictures, an extremely dangerous duty. by geekteam6
From his IMBD trivia page: https://m.imdb.com/name/nm0456158/trivia
Jack Kirby was famous for being as tough as his characters. For instance, when a gangster was shaking down Kirby's boss, Will Eisner, to take his towel service, Kirby charged in to throw the gangster out. When Kirby created Captain America with Joe Simon, Nazi sympathizers once gathered in the lobby of the office building where the pair worked to threaten them. However, when upon hearing that Kirby was heading down with his sleeves rolled up to physically confront them himself, they fled before he arrived.