U.D.O. is a German heavy metal band founded by lead singer Udo Dirkschneider in 1987. 　　After Udo Dirkschneider left Accept in 1987, a large fan community followed him to U.D.O. 　　Starting with the first two albums Animal House in 1987 and Mean Machine in 1988, U.D.O. proved to be pure heavy metal without any Trend-Sound influences. Both albums continued where Accept had left off in 1986 with Russian Roulette. Apart from U.D.O., Animal House was recorded by Peter Szigeti (guitars), Frank Rittel from Warlock on (bass), Mathias Dieth from Sinner and Gravestone (guitars) and Thomas Franke (drums). 　　From 1987 to 1989, they toured with the following line-up: Udo Dirkschneider (vocals), Mathias Dieth (guitar), Andy Susemihl (guitar), Dieter Rubach (bass) and Thomas Franke (drums). They toured with Guns N' Roses, Lita Ford and Zodiac Mindwarp. 　　By Mean Machine, the band had a different line-up: only Udo Dirkschneider, Mathias Dieth and Andy Susemihl remained. New additions were Thomas Smuszynski (bass) and Stefan Schwarzmann (drums). 　　U.D.O. achieved success with the album Faceless World, produced by ex-Accept drummer Stefan Kaufmann. U.D.O.'s follow-up album was Timebomb in 1991 and it was their last for five years.