Earth-Two (also Earth Two or Earth 2) is a setting for stories (a "fictional universe") appearing in American comic books published by DC Comics. First appearing in The Flash #123 (1961), Earth-Two was created to explain differences between the original Golden Age and then-current Silver Age versions of characters such as the Flash, and how the current (Earth-One) versions could appear in stories alongside earlier versions of the same character concepts. Earth-Two includes DC Golden Age heroes, including the Justice Society of America, whose careers began at the dawn of World War II, concurrently with their first appearances in comics. Earth-Two, along with the four other surviving Earths of the DC Multiverse, were merged into one in the 1985 miniseries Crisis on Infinite Earths. However, following the events of Infinite Crisis, the Multiverse was reborn, although the subsequent Earth-Two was not the same as its pre-Crisis equivalent. Following the events of Flashpoint, the setting was revised once again, and was now identified as "Earth 2" (instead of "Earth Two" or "Earth-Two"). While it still houses a team of superheroes, its membership is younger than before. Earth 2 also has a tragic backstory, having been invaded by an alien horde from Apokolips five years prior to the reboot, ahead of Darkseid's attempted invasion of Prime Earth. In the process, this reality's Superman, Batman and Wonder Woman all died, while its Supergirl and Robin were swept through a dimensional warp to Prime Earth where they became known as Power Girl and Huntress. Publication history Introduction ("Flash of Two Worlds") Characters from DC Comics were originally suggestive of each existing in their own world, as superheroes never encountered each other. This was soon changed with alliances being formed between certain protagonists. Several publications, including All Star Comics (publishing tales of the Justice Society of America), Leading Comics (publishing tales of the Seven Soldiers of Victory) and other comic books introduced a "shared universe" among several characters during the 1940s. By the 1950s, as the popularity of superheroes was waning, comics shifted to horror, westerns and war. Batman, Superman and Wonder Woman were among the few DC continued to publish. Beginning in the early 1960s, the popularity of superheroes began to grow. DC introduced more modern versions of its heroes. For example, Hawkman was an alien policeman instead of a reincarnated Egyptian prince. Older versions of DC characters were assigned to an "alternative reality"