Otto II, Holy Roman Emperor

Otto II was born in 955, the youngest and only surviving son of Otto the Great and Adelaide of Italy. His father made him joint-ruler of Germany at six and co-Emperor at twelve to lock in the succession, then arranged his marriage to the Byzantine princess Theophanu. When Otto the Great died in 973 after thirty-seven years, Otto II took absolute power at eighteen without contest. Early on he crushed a revolt from rival branches of the Ottonian dynasty claiming the throne, a victory that let him cut the Bavarian line out of succession and secure the crown for his own son. From 980 he turned south, determined to absorb all of Italy into the Empire - a campaign that put him on collision course with Byzantium and the Fatimid Caliphate. After early gains among the Lombard principalities, his southern offensive collapsed in 982 with a catastrophic defeat by Muslim forces. While he prepared a counterattack, a massive Slav uprising erupted in 983, forcing the Empire to abandon its holdings east of the Elbe. Otto II died suddenly in December 983 at twenty-eight, ten years into his reign, leaving his three-year-old son Otto III as Emperor and the realm in upheaval.