Achtung Baby ( ) their 1988 double album and documentary film Rattle and Hum precipitated a critical backlash. Although the record sold 14 million copies and performed well on music charts, critics were dismissive of it and the film, labelling the band's exploration of early American music as "pretentious" and "misguided and bombastic". U2 believed that audiences misunderstood the group's collaboration with blues musician B. B. King on Rattle and Hum and the Lovetown Tour, and they described it as "an excursion down a dead-end street". During a 30 December 1989 show near the end of the Lovetown Tour, Bono said on stage to the hometown crowd in Dublin that it was "the end of something for U2", and that "we have to go away and ... dream it all up again". Following the tour, the group began what was at the time their longest break from public performances and album releases.
Reacting to their own sense of musical stagnation and to their critics, U2 searched for new musical ground. They had written "God Part II" from Rattle and Hum after realising they had excessively pursued nostalgia in their songwriting. The song had a more contemporary feel that Bono said was closer to Achtung Babys direction. Further indications of change were two recordings they made in 1990: the first was a cover version of "Night and Day" for the first Red Hot + Blue release, in which U2 used electronic dance beats and hip hop elements for the first time; the second indication of change was contributions made by Bono and guitarist the Edge to the original score of A Clockwork Oranges stage adaptation. Much of the material they wrote was experimental, and according to Bono, "prepar[ed] the ground for Achtung Baby". Ideas deemed inappropriate for the play were put aside for the band's use. During this period, Bono and the Edge began increasingly writing songs together without Mullen or bassist Adam Clayton. The demos later evolved into the songs "Who's Gonna Ride Your Wild Horses", "Until the End of the World", "Even Better Than the Real Thing", and "Mysterious Ways". Going into the album sessions, U2 wanted the record to completely deviate from their past work, but they were unsure how to accomplish it. Lanois was principal producer, with Mark "Flood" Ellis as engineer. Eno said his role was "to come in and erase anything that sounded too much like U2". By distancing himself from the work, he believed he provided the band with a fresh perspective on their material each time he rejoined them. Since U2 wanted the record to be harder-hitting and live-sounding, Lanois "push[ed] the performance aspect very hard, often to the point of recklessness". The Lanois–Eno team used lateral thinking and a philosophical approach—popularised by Eno's Oblique Strategies—that contrasted with the direct and retro style of Rattle and Hum producer Jimmy Iovine. They chose to record at Hansa Studios in West Berlin, near the recently opened Berlin Wall. Several acclaimed records were made at Hansa, including two from David Bowie's "Berlin Trilogy" with Eno, and Iggy Pop's Lust for Life. Expecting to be inspired in Berlin, U2 instead found the city to be depressing and gloomy. The collapse of the Berlin Wall had resulted in a state of malaise in Germany. The band found their East Berlin hotel to be dismal and the winter inhospitable, while the location of Hansa's Studio 2 in a former SS ballroom, the Meistersaal, added to the "bad vibe". The Edge had been listening to electronic dance music and to industrial bands like Einstürzende Neubauten, Nine Inch Nails, the Young Gods, and KMFDM. He and Bono advocated new musical directions along these lines. In contrast, Mullen was listening to classic rock acts such as Blind Faith, Cream, and Jimi Hendrix, and he was learning how to "play around the beat".
U2 is credited with composing the music for all of Achtung Babys tracks, industrial music, The band referred to the album's musical departure as "the sound of four men chopping down The Joshua Tree".
thumb|right|alt=|The Edge on the Zoo TV Tour in November 1993
For the album, the Edge often eschewed his normally minimalistic approach to guitar playing and his trademark chiming, delay-heavy sound, in favour of a style that incorporated more solos, dissonance, and feedback. Industrial influences and guitar effects, particularly distortion, contributed to a "metallic" style and "harder textures". for what Bono called "U2 at our funkiest... Sly and The Family Stone meets Madchester baggy."—the timbre of Mullen's drums exhibits a "cold, processed sound, something like beating on a tin can", according to author Albin Zak.
Whereas Bono exhibited a full-throated vocal delivery on the group's previous releases, for Achtung Baby he extended his range into a lower register and used what Fast described as "breathy and subdued colors". one technique used is octave doubling, in which the vocals are doubled but sung in two different octaves. This octave differentiation was sometimes done with vocals simultaneously, while at other times, it distinguishes voices between the verses and choruses. According to Fast, the technique introduces "a contrasting lyrical idea and vocal character to deliver it", leading to both literal and ironic interpretations of Bono's vocals. He said that lowering his voice helped him find a new vocal vocabulary, as he previously felt limited to "certain words and tones" by his tenor voice. Other methods of altering his vocals included treating them with processing
As is often the case on U2 albums, Bono is credited as the sole lyricist. The lyrics are darker in tone, describing troubled personal relationships and exuding feelings of confusion, loneliness, and inadequacy. Lyrics were inspired by the dissolution of the Edge's marriage, as well as that of another of Bono's friends. During the album's recording, the Edge separated from his wife (the mother of three of his children), and the pain he felt resulted in him dedicating himself to the record and advocating for more personal themes. Bono found inspiration from his own personal life, citing the births of his two daughters in 1989 and 1991 as major influences. The Edge described the song on one level as a "bitter, twisted, vitriolic conversation between two people who've been through some nasty, heavy stuff". and on "Acrobat", Bono sings about weakness, hypocrisy, and inadequacy. The torch songs of Roy Orbison, Scott Walker, and Jacques Brel were major influences, and the closing track, "Love Is Blindness", a bleak account of a failing romance. Flanagan interpreted Achtung Baby as using the moon as a metaphor for a dark woman seducing the singer away from his virtuous love, the sun; he is tempted away from domestic life by an exciting nightlife and tests how far he can go before returning home. For Flanagan, "Tryin' to Throw Your Arms Around the World" on the album's latter third describes the character stumbling home in a drunken state, and the final three songs—"Ultraviolet (Light My Way)", "Acrobat", and "Love Is Blindness"—are about how the couple deal with the suffering they have forced on each other. This reflects the group's revisiting some of the Dadaist characters and stage antics they dabbled with in the late 1970s as teenagers but abandoned for more literal themes in the 1980s. While the band had previously been opposed to materialism, they examined and flirted with this value on the album and the Zoo TV Tour. juxtaposed against the dark lyrics in the verses.
Religious imagery is present throughout the record. "Until the End of the World" is an imagined conversation between Jesus Christ and his betrayer, Judas Iscariot. In many tracks, Bono's lyrics about women carry religious connotations, describing them as spirits, life, light, and idols to be worshipped. Religious interpretations of the album are the subject of the book Meditations on Love in the Shadow of the Fall from the 33 ⅓ series.