[1][2] His father, Romanos Kourkouas, was a senior military commander in the 960s,[3] and the son of the great general John Kourkouas,[4] who held the post of Domestic of the Schools (commander-in-chief of the Byzantine army) for 22 years and led the Byzantine armies against the Muslim border emirates in the period 926–944.
[6] John is first mentioned in 970, during the Byzantine campaigns in Bulgaria in the aftermath of the invasion by Sviaroslav of Kievan Rus'.
[7][9] According to the contemporary historian Leo the Deacon, he was inexperienced, and prone to idleness and drunkenness, and thus encouraged the Rus' to persist in their raids into the Byzantine territories in Thrace.
[7][9] After the suppression of Phokas' revolt, in summer 971, Tzimiskes himself set out at the head of the imperial army against the Rus'.
[9][8] Leo the Deacon claims that he had been drunk and, and just received an imperial reprimand for having pillaged churches in Bulgaria.