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 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.