Batman - Early years

Batman made his debut in Detective Comics #27 (May 1939). Cover art by Bob Kane.

The first Batman story, "The Case of the Chemical Syndicate," was published in Detective Comics #27 (May 1939). Finger said, "Batman was originally written in the style of the pulps", and this influence was evident with Batman showing little remorse over killing or maiming criminals and was not above using firearms. Batman proved a hit character, and he received his own solo title in 1940, while continuing to star in Detective Comics. By that time, National was the top-selling and most influential publisher in the industry; Batman and the company's other major hero, Superman, were the cornerstones of the company's success. The two characters were featured side-by-side as the stars of World's Finest Comics, which was originally titled World's Best Comics when it debuted in fall 1940. Creators including Jerry Robinson and Dick Sprang also worked on the strips during this period.

Over the course of the first few Batman strips elements were added to the character and the artistic depiction of Batman evolved. Kane noted that within six issues he drew the character's jawline more pronounced, and lengthened the ears on the costume. "About a year later he was almost the full figure, my mature Batman," Kane said. Batman's characteristic utility belt was introduced in Detective Comics #29 (July 1939), followed by the boomerang-like batarang and the first bat-themed vehicle in #31 (Sept. 1939). The character's origin was revealed in #33 (Nov. 1939), unfolding in a two-page story that establishes the brooding persona of Batman, a character driven by the loss of his parents. Written by Finger, it depicts a young Bruce Wayne witnessing the death of his parents as part of a street robbery. Days later, at their grave, the child vows that "by the spirits of my parents [I will] avenge their deaths by spending the rest of my life warring on all criminals".

The early, pulp-inflected portrayal of Batman started to soften in Detective Comics #38 (April 1940) with the introduction of Robin, Batman's kid sidekick. Robin was introduced, based on Finger's suggestion Batman needed a "Watson" with whom Batman could talk. Sales nearly doubled, despite Kane's preference for a solo Batman, and it sparked a proliferation of "kid sidekicks". The first issue of the solo spin-off series Batman was notable not only for introducing two of his most persistent antagonists, the Joker and Catwoman, but for a story in which Batman shoots some monstrous giants to death. That story prompted editor Whitney Ellsworth to decree that the character could no longer kill or use a gun.

By 1942, the writers and artists behind the Batman comics had established most of the basic elements of the Batman mythos. In the years following World War II, DC Comics "adopted a postwar editorial direction that increasingly de-emphasized social commentary in favor of lighthearted juvenile fantasy." The impact of this editorial approach was evident in Batman comics of the postwar period; removed from the "bleak and menacing world" of the strips of the early 1940s, Batman was instead portrayed as a respectable citizen and paternal figure that inhabited a "bright and colorful" environment.