Some have referenced that his mother was already pregnant with Marwan before his legal father, Muhammad, bed her, thus making the child not his.

[4][incomplete short citation] These two men were believed to be Marwan's real biological father by Umayyad contenders.

In 735–736, Marwan invaded Georgia, devastated it and then took three fortresses of the Alans and made peace with Tumanshah.

In 744–745, on hearing news of the plot to overthrow al-Walid II, Marwan wrote to his relatives from Armenia strongly discouraging this.

He urged them to harmoniously preserve the stability and well-being of the Umayyad house, however, this was disregarded and many armed men moved into Damascus.

Yazid slipped into Damascus and deposed al-Walid in a coup, following this up with a disbursement of funds from the treasury.

[6] Reportedly, Marwan II, who for several years had supervised the campaigns against the Byzantines and the Khazars on the Caliphate's northwestern frontiers, had considered claiming the caliphate at the death of al-Walid II, but a Kalbi rebellion had forced him to wait.

Instead, Yazid III appointed him governor to Upper Mesopotamia and he took up residence in the Qays-dominated city of Harran.

When Yazid III persisted in overthrowing al-Walid II, Marwan at first opposed him, then rendered allegiance to him.

Al-Dahhak's successor al-Khaybari was initially successful in pushing back Marwan's center and even took the caliph's camp and sat on his carpet.

In Khurasan there was internal discord, with the Umayyad governor Nasr ibn Sayyar facing opposition from al-Harith and al-Kirmani.

Marwan fled, leaving Damascus, Jordan and Palestine and reaching Egypt, where he was caught and killed on 6 August 750.