John I Tzimiskes shi ne babban Sarkin Rumawa daga 11 ga Disamba 969 zuwa 10 Janairu 976. Janar mai basira da nasara, ya karfafa daular kuma ya fadada iyakokinta a cikin gajeren mulkinsa.Ba da jimawa ba aka tabbatar da yankin Aleppo a karkashin yarjejeniyar Safar.A cikin jerin kamfen da Kievan Rus ya yi a kan Lower Danube a cikin 970-971, ya kori abokan gaba daga Thrace a yakin Arcadiopolis, ya haye Dutsen Haemus, ya kewaye kagara na Dorostolon (Silistra) a Danube. tsawon kwanaki sittin da biyar, inda bayan yaƙe-yaƙe da yawa ya yi nasara a kan Babban Yarima Svyatoslav na Rus.A cikin 972, Tzimiskes ya juya zuwa ga Daular Abbasid da vassals, farawa da mamayewa na Upper Mesopotamiya .Yaƙin neman zaɓe na biyu, a shekara ta 975, an nufi Siriya, inda sojojinsa suka ci Homs, Baalbek, Damascus, Tiberias, Nazarat, Kaisariya, Sidon, Beirut, Byblos, da Tripoli, amma sun kasa ci Urushalima.