The Muslim civil war left the Umayyad realm restricted to Damascus and its environs after most of their territories came under Ibn al-Zubayr's orbit.

However, an Umayyad resurgence began with the accession of Caliph Marwan I, who dispatched an army led by Ubayd Allah ibn Ziyad to reconquer Iraq.

This army's advance into Mosul precipitated the Battle of Khazir and its commander, Ubayd Allah, was an enemy of Mukhtar's pro-Alid partisans.

During the initial combat, part of Ibn al-Ashtar's forces were put to flight, but then regrouped under his command and charged against the Umayyad center.

Meanwhile, the blood feud between the Qaysi and Yamani tribal elements of the Umayyad Caliphate intensified due to Umayr's mid-battle defection and subsequent spearheading of attacks against the tribes of Taghlib and Kalb.

[1] In the aftermath, they lost authority over Iraq (the part of Mesopotamia south of Tikrit[2]) while the governors of northern Syria and Palestine switched their allegiance to Abd Allah ibn al-Zubayr, the anti-Umayyad claimant to the caliphate.

[4] As a result of his efforts and the consensus of loyalist Arab tribes, later collectively known as the "Yaman", the Umayyad elder, Marwan ibn al-Hakam, became caliph in June 684.

[3][6] Control of that region was split by a number of anti-Umayyad factions, including the partisans of Mukhtar al-Thaqafi, other pro-Alids (supporters of Caliph Ali and his family) and Ibn al-Zubayr.

[3] In the eighteen months following the Umayyad victory at Ayn al-Warda, Ubayd Allah's troops were bogged down by struggles with the Qaysi tribes of the Jazira (Upper Mesopotamia) led by the pro-Zubayrid Zufar ibn al-Harith al-Kilabi.

[6][7] In the summer of 686, Ubayd Allah's troops advanced toward Mosul,[8] long controlled by a Kufan military elite,[9] with the ultimate aim of conquering Iraq.

[10] The ranks of Ubayd Allah's 60,000-strong army consisted of Arab tribesmen from Syria and as such was referred to in medieval sources as jumū' ahl al-Shām (host of the Syrians).

[11] Historian Hugh N. Kennedy asserts that this "report is exaggerated" because Ubayd Allah recruited commanders from both Qays and Yaman (the latter were dominated by the Kalb), "but it does point to a general problem" regarding the effect of the Qaysi–Yamani rivalry on the Umayyad army.

[16] The ranks of the mawālī were dominated by the Persians of Kufa led by Abu Amra Kaysan;[16] the latter, a mawlā of a Bajila tribesman, either commanded the shurṭa or the ḥaras (personal guard) of Mukhtar.

[16][18] In early August 686, the entire body of Ibn al-Ashtar's forces marched north toward the Zab River to block the Umayyad army's advance into Iraq.

[22] Al-Saluli exchanged words and insults with one of Ubayd Allah's soldiers and returned to Ibn al-Ashtar with news that the Umayyads were in "a state of confusion and dismay".

[22] Ibn al-Ashtar then reviewed his troops and rallied them to fight a jihad (holy war) against the "murderer of Husayn", i.e. Ubayd Allah.

[28] Mukhtar and his supporters viewed Ubayd Allah's death as justice for his role in the killing of Husayn ibn Ali at Karbala in 680.

[10] Abd al-Malik desisted from further attempts to conquer Iraq following the debacle at Khazir, and instead focused on winning over disaffected tribal chieftains throughout the province.