Fighting under the command of his fellow Sulaymi tribesman, Safwan ibn Mu'attal,[4] Umayr played an instrumental role in the Umayyads' capture of an Armenian fortress known as "Ḥiṣn Kamkh" (Kamacha) in 678.
Umayr was rewarded by Ibn al-Ashtar, al-Mukhtar's governor over Mosul and the Jazira, with the local governorships of Tur Abdin and Kfartutha (Kafr Tuta).
[6] He or Zufar led a Qaysi raid against the Kalb at Iklil in the Samawah desert between Syria and Iraq, killing between 500 and 1,000 Kalbi tribesmen.
[7] Umayr's energetic entry into the Qays–Kalb feud made him the more active leader of the Qays, as Zufar was often bogged down defending Qarqisiya from Umayyad advances.
[8] Meanwhile, Umayr entangled the Qays into a bloody tit-for-tat war with the previously neutral Taghlib tribe when he led Sulaymi encroachments into Taghlibi territory along the Khabur River.
[9] Raids and counter-raids followed at places straddling the Khabur, Balikh, Tigris and Tharthar rivers, with the Taghlib typically being the beaten force.