It’s more or less an objective qualification that The Joshua Tree is the paradigmatic U2 album. Achtung Baby is, on the other hand, their best and most interesting, densest and most mature, and perhaps a different album than how it’s often discussed. After the backlash to Rattle and Hum, the band felt like they needed to take a breather and “dream it all up again,” resulting in the longest hiatus they’d had between albums up until that point. When U2 did reemerge, it was as an entirely different band, one intent on blowing up its old image with dance beats, processed and mutated guitars, and sly winks and self-deprecating humor supplanting their full-throated earnestness of the ’80s.

They almost never made it there, though. Recording for Achtung Baby began in Berlin, the band believing they needed to remove themselves from the usual family routine of their lives in Ireland, and that it’d be an inspiring time to be in Germany as the Berlin Wall finally came down. What resulted was one of the most difficult phases of the band’s life. There was a sharp division among those involved regarding what direction this new record should take and it was Bono and the Edge who were pushing for starting anew with a fresh sound and aesthetic. Each had grown fascinated with club culture and dance music, and the Edge was inspired by the mechanistic nature of industrial music as well as the way bands like My Bloody Valentine and Sonic Youth were breaking new ground with the sounds they coaxed out of their guitars. Daniel Lanois had come onboard expecting to produce the same U2 he’d worked with just a few years earlier on The Joshua Tree and was confused by this new direction. His frustrations were shared by Clayton and Mullen, who preferred to stick with what U2 had been doing. Mullen was particularly lost, as he’d been listening to classic rock and felt threatened by the idea of incorporating dance elements into U2’s music. The inter-band strife was compounded by the fact that it was becoming difficult to make songs cohere into finished products, and the fact that the Edge and Bono had taken to writing more just the two of them, where the band had previously written by jamming together.

As the story goes, the Edge crammed two leftover chord progressions together and came up with the bare bones of “One,” which the band then improvised into existence. The ease of its creation changed the timbre of the sessions, and the members often credit it as the single song that wound up keeping them together. The process was far from over, but when Achtung Baby finally saw release in 1991 it was one of the most successful reinventions in 20th century pop music.

A lot of the album was an intentional put-on. Fixated on distancing themselves from the ponderousness of their late ’80s image, the band eventually embraced the trashy pop pastiche Bono and the Edge were advocating. The album’s more sardonic title was chosen specifically to avoid it seeming another solemn U2 album in the mode of The Joshua Tree. In this regard, all the things people say about ’90s U2 are true. They became more performative, with Bono becoming interested in creating characters like the Fly to impersonate during live performances. They became ironic, abandoning the lofty symbols and spirituality of their previous work and trafficking in all the crasser qualities of pop culture.

Some have suggested that this means U2’s ’90s work was disingenuous in some way. This is the reductive behavior I was referring to before. Achtung Baby announced a reinvention that’d define the band’s second decade, but rather than their postmodern hijinks being a signal that U2 had become a self-detached cartoon, they actually pointed to how complex their music had become. Achtung Baby might’ve marked where U2 got less serious about their image, but their lyrics were never as introspective as they were here. Personal issues (the Edge had separated from his wife) and major life changes (Bono had become a father) turned their gaze inward, eschewing the big political visions of their past. Like the title, the beginning of the album was designed to confront. The distorted snarl of the Edge’s guitar was just one instance of what Bono described as “the sound of four men chopping down The Joshua Tree.” But, like Achtung Baby as a whole, while its intention was to provoke, its heart was honest: it’s a song about new beginnings, Bono narrating another birth for U2 at the start of a new decade under the metaphor of Berlin. While other songs like “The Fly” or “Even Better Than the Real Thing” pushed the band’s sounds in similar ways, other tracks felt like vintage U2 updated with a new sheen. “Who’s Gonna Ride Your Wild Horses?” and “Ultraviolet (Light My Way)” felt different, but also like they made sense in the larger context of the band’s work; tracks like these were not jarring, but were a definitive progression. “Until the End of the World,” perhaps the best song the band ever wrote, is somewhere in between, a definitively ’90s U2 track that is nevertheless devoid of any of the wicked smirks of that era, preferring instead the complicated narrative of combining a conversation between Jesus and Judas with questions of sexuality in order to form a overarching story of betrayal and the malleability of identity.

Achtung Baby is the kind of album that has any number of reasons it shouldn’t have even happened. Everything seemed to be working against it, and it should have been at least a mild failure. And yet, it’s remained U2’s most engaging album for over 20 years now.