The Dark Knight Universe began with Frank Miller’s 1986 four-issue prestige-format mini-series The Dark Knight (later known as The Dark Knight Returns), which he wrote and penciled, with Klaus Janson providing inks. The story depicted a Batman returning from retirement in a Cold War milieu. Soon after, Miller wrote the “Year One” storyline, illustrated by David Mazzucchelli and serialized over four issues of Batman. The story radically re-envisioned Batman’s earliest days in a gritty, realistic, and street-level tale. Both stories proved hugely influential, especially over Batman’s subsequent development. While The Dark Knight Returns was an alternate-reality story, “Year One” was officially part of DC’s main continuity from the time of its publication until DC’s 2011 relaunch.

In 1994, Miller returned to Batman with Spawn / Batman, a one-shot, illustrated by Todd McFarlane, that took place sometime between “Year One” and Batman’s retirement. Miller has stated that he considers this part of his Dark Knight Universe, although it was published by Image Comics and has not been republished by DC Comics. Because of this, the story’s short length, and the fact that it is referenced in other Spawn stories but is insignificant to the rest of the Dark Knight Universe, the one-shot is best understood as part of Spawn’s continuity, rather than the Dark Knight Universe. However, it may be understood as a part of the Dark Knight Universe that is canonical to two continuities, not unlike how “Year One” was also canonical to DC’s main universe.

Miller again returned to the Dark Knight Universe for 2001-2002′s The Dark Knight Strikes Again, a sequel to The Dark Knight Returns, which he both wrote and illustrated. By 2001, The Dark Knight Returns had long been considered a classic, and the idea of a sequel was shocking to fans (this was prior to the production of prequels to Watchmen, a classic of similar stature). Published as three massive issues (each nearly twice as long as an issue of The Dark Knight Returns), the series sold very well but was widely panned.

In 2005, Miller began All Star Batman and Robin, the Boy Wonder, illustrated by Jim Lee. The series was set not long after “Year One” and featured the origin of Robin. Like The Dark Knight Strikes Again, the series sold well but was widely panned. In the second issue, Batman referred to himself as “the Goddamned Batman” in order to intimidate the future Robin, and this quotation quickly became a meme that seemed to represent the over-the-top toughness of this version of Batman. The series also came under criticism for sexism, especially given that Frank Miller’s script for the first issue called for a close-up of a female character’s butt. In addition, an alternate cover by Miller was nothing more than Wonder Woman’s rear end, and virtually every female character in the series was defined sexually. The series ultimately lasted ten issues, several of which were delayed. Issue #10, published in 2008, began what was to have been the title’s second story arc — although the story’s title was simply “Episode Ten,” in line with previous story titles, suggesting that this division into story arcs was an artificial one, made in part for the purposes of collected editions. This final issue also had to be pulped and reprinted. Miller had requested that profanity in his script be lettered as written and censored with black bars after the fact; however, DC discovered that the printed issue’s black bars were not entirely opaque, allowing the profanity beneath them to be read. The company pulped and reprinted the issue. With the exception of the delay caused by this incident, Lee took the blame for the delays on the title, saying that Miller had written in advance of what had been illustrated. In April 2010, DC announced that the remaining issues would be published, in 2011, as a separate six-issue mini-series entitled Dark Knight: Boy Wonder. However, Lee abandoned the project in favor of Justice League, relaunched that year, and the story has never been completed.

In 2006, during the early issues of All Star Batman and Robin, Miller announced that he was working on a graphic novel entitled Holy Terror, Batman! This title mixes a reference to the 1960s Batman TV show, on which Robin often used similar expressions (with various words in the place of “terror”), with a reference to religiously inspired terrorism. Miller announced that the story, set between “Year One” and All Star Batman and Robin, was to feature Batman pursuing Osama bin Laden, in a nod to “propagandistic” moments in World War II super-hero comics. During production, however, Miller changed the protagonist from Batman to the Fixer, a Batman analog. Similar analogs to Batman’s cast may be seen throughout the graphic novel, which was finally published simply as Holy Terror in September 2011, just slightly more than 10 years after 9/11. Holy Terror may thus be seen as a non-canonical volume of the Dark Knight Universe. While some praised the book, it was widely denounced by smarter critics as Islamophobic. Some critics had pointed out fascistic and sexist strains in The Dark Knight Returns and “Year One” since their publication, and the negative reaction to The Dark Knight Strikes Again and All Star Batman and Robin helped make more people open to such criticism.

Despite this, Miller returned to the Dark Knight Universe again for 2015-2016′s Dark Knight III: The Master Race. For the first time, a volume in the Dark Knight Universe wasn’t written entirely by Miller; The Master Race was co-written by Brian Azzarello. In addition to the main, regular-length story, each issue also featured a shorter, inset comic book starring a different character, intended to flesh out the Dark Knight Universe. Before the series began, Miller stated that working on it had gotten him excited to produce a third sequel.

Originally, the notion that “Year One” and The Dark Knight Returns existed in the same universe was highly theoretical, since “Year One” was part of the main DC Universe’s continuity, while The Dark Knight Returns was not. The two works were consistent with one another, yet weren’t technically set in the same continuity. Plenty of fans and scholars praised and studied Miller’s take on Batman, and readers of The Dark Knight Returns were free to imagine that its Batman had once experienced what was depicted in “Year One,” but this wasn’t officially the case. Miller clearly saw the two works (and later, Spawn / Batman) as portraying his singular version of Batman, but such statements are not uncommon for creators, even when their works unambiguously feature different incarnations of a particular character. The Dark Knight Strikes Again didn’t change this situation, since it clearly took place in the same universe as The Dark Knight Returns, while “Year One” was still more or less part of DC’s main continuity. At first, it wasn’t clear whether All Star Batman and Robin, the Boy Wonder was officially set in an “All Star” universe, in which it would have shared continuity with All Star Superman. This would have meant that Miller’s Batman work officially took place in three separate continuities: the main DC Universe, an All Star continuity, and the alternate continuity of The Dark Knight Returns. Once the All Star line failed to expand as planned, DC officially announced that it wasn’t a separate universe but a showcase for major creators. Thus, All Star Batman and Robin, the Boy Wonder was officially set in a universe in which only Miller’s Batman stories took place, exactly as Miller had imagined. In 2007, this Dark Knight Universe was canonized as one of DC’s 52 alternate universes. After DC’s 2011 reboot of its multiverse, a new version of Batman’s origins, titled “Zero Year,” unambiguously rendered “Year One” no longer canonical, or even semi-canonical. While “Year One” remains canonical to DC’s post-Crisis on Infinite Earths continuity, new stories were no longer being produced for that continuity, whereas Miller’s Dark Knight Universe continued to expand. In this way, the concept of a Dark Knight Universe took hold gradually, evolving from a theoretical construct to official policy, in large part because Miller kept returning to Batman. Despite its sporadic publication schedule, Miller’s Dark Knight Universe simply survived DC’s own.

Taken as a whole, the Dark Knight Universe currently comprises five volumes — two set during Batman’s early years and three set during and after Batman’s return. One issue of an additional volume set during Batman’s early years – or an expansion of a current volume, depending on your point of view — has been published, but that story has never been completed. All of this material was written by Frank Miller, with the exception of The Master Race, which was co-written by others, primarily Brian Azzarello. Miller illustrated two of these volumes himself, one in collaboration with Klaus Janson.

While the Dark Knight Universe has grown into its own identity, it doesn’t read as a coherent whole, largely due to stylistic differences between its various volumes, which were sometimes produced decades apart. For example, reading the volumes in chronological order would result in the very controlled and compressed “Year One,” which features no super-powers, followed by the comparatively decompressed and over-the-top All Star Batman and Robin, which features several other characters with super-powers. Nonetheless, these two works are united by certain themes, including violence, corruption, sexualization, and a depiction of Batman at war with the world around him. It may be best to think of the Dark Knight Universe less as a single, coherent story in multiple volumes and more as a series of somewhat different, strong takes on Batman, loosely set in the same universe.