 In 969, Emperor Otto I entered into an alliance with Byzantine Emperor John I Tzimiskes in which both Eastern and Western Empires would jointly-govern southern Italy.Otto I's death in 973 and John I's death in 976 caused this alliance to deteriorate.Otto I's successor in the West, his son Emperor Otto II, and John I's successor in the East, his nephew Emperor Basil II, brought the two Empires once again into conflict over control of southern Italy.