They "won" the first Muslim civil war, beating out Muhammad's son-in-law, Ali, and Mu'awiyah, the son of Abu Sufyan, was the first ruler of this polity.
Only one ruler of this group was later recognized as a caliph and not merely a secular king; that ruler is Abd al-Aziz. His father dealt with the rebellions by al-Mukhtar in Kufa and the combined forces of the Kharijites, Shi'ah, and Abd Allah ibn az-Zubayr in Iraq. This group was split between the Sufyanids, whose first leader attempted the first siege of Constantinople, and the Marwanids, whose last ruler, Marwan II, died at the Battle of the Great Zab River. They "won" the first Muslim civil war, beating out Muhammad's son-in-law, Ali, and Mu'awiyah, the son of Abu Sufyan, was the first ruler of this polity. Ruling out of Damascus, for 10 points, what is this second Islamic caliphate?
Only one ruler of this group was later recognized as a caliph and not merely a secular king; that ruler is Abd al-Aziz.
{Umayyad} caliphate [or {dynasty}]