In his 1939 debut, Batman frequently used guns and killed criminals without hesitation.

Batman first appeared in Detective Comics #27, published in May 1939, created by Bob Kane and Bill Finger. The character drew heavy inspiration from pulp fiction heroes like The Shadow, and in these early stories, Batman was a cold-blooded vigilante who carried a .45 caliber pistol and showed little remorse for killing his enemies.A turning point came in Batman #1, published in spring 1940, when Batman used a machine gun mounted on his Batplane to kill a group of monstrous giants—henchmen of the villain Hugo Strange. The graphic violence alarmed editor Whitney Ellsworth, who worried the character would become a negative influence on the growing youth audience.In response, Ellsworth introduced strict editorial guidelines forbidding Batman from killing or using firearms. This shift coincided with the introduction of Robin, the Boy Wonder, in Detective Comics #38. The new sidekick was designed to soften Batman's image and provide a relatable character for younger readers.By the mid-1940s, the "no-kill" rule had become central to Batman's moral code. This constraint pushed writers to emphasize his detective skills and martial arts mastery instead of raw violence. Today, his refusal to use guns stands as one of his most iconic traits, often explained as a psychological response to witnessing his parents' murder by gunfire.