Crisis on Earth-Two

A crisis in the DC Universe is an event with potentially great consequences, often involving multiple universes and sometimes even threatening their existence.

From 1963 to 1985 the term "crisis" was used to describe the annual events in which the Justice League of America of Earth-One and the Justice Society of America of Earth-Two met and worked together, usually in an incident involving one or more of the parallel worlds of the DC Multiverse. This usage culminated in 1985's year-long Crisis on Infinite Earths, in which the Multiverse was eliminated. After several years of disuse, the term "crisis" was applied to several events with either "universal" stakes or substantial character consequences, such as Zero Hour: Crisis in Time!, Infinite Crisis, and Final Crisis.

In the two decades after 1985, "Crisis" by itself came to refer specifically to Crisis on Infinite Earths, especially when used in house pre-Crisis and post-Crisis.

Characters in the DC Universe sometimes use the term "crisis" in the same sense, referring either to any great threat, or as "the Crisis" in reference to the events of Crisis on Infinite Earths, either as they happened or as they were commonly remembered in the revised history after the fact.

With the publication of Infinite Crisis, and Final Crisis, the use of the term within the DC Universe has shifted. The Crisis on Infinite Earths is sometimes referred to as "the first Crisis". The Infinite Crisis has occasionally been referred to as simply "the crisis", and a character from the 31st century called it "the middle Crisis"

This story served as a prelude to the Crisis saga as it introduced the idea of the Multiverse to the public's mind and would eventually lead to the later Crisis stories.

This story can be found in The Flash #123.

Although there may have been other DC Comics stories with "crisis" in the title before "Crisis on Earth-One!", it was this issue that started the tradition of the annual JLA/JSA crossover, which usually had the word "crisis" in the title of at least one of its issues.

"Crisis on Earth-One!" and "Crisis on Earth-Two!" was the first story in which the JLA and JSA met as teams. Members of the two teams would meet once each year after this until Crisis on Infinite Earths in 1985.

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