After the death of his guardian John I Tzimiskes, Basil II became the effective ruler and senior emperor of the Byzantine Empire.

John I Tzimiskes was the senior Byzantine emperor from 969 to 976. An intuitive and successful general who married into the influential Skleros family, he strengthened and expanded the Byzantine Empire to include Thrace and Syria by warring with the Rus' under Sviatoslav I and the Fatimids respectively.

Basil II Porphyrogenitus, nicknamed the Bulgar Slayer, was the senior Byzantine emperor from 976 to 1025. He and his brother Constantine VIII were crowned before their father Romanos II died in 963, but they were too young to rule. The throne thus went to two generals, Nikephoros Phokas and John Tzimiskes before Basil became senior emperor, though his influential great-uncle Basil Lekapenos remained as the de facto ruler until 985. His reign of 49 years and 11 months was the longest of any Roman emperor.

The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the events that caused the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'.