This empire's decline was
This empire's decline was hastened when frontier warriors at Merv rebelled. This empire was defeated by Leo the Isaurian at the Battle of Akroinon, where their troops were commanded by Hisham, and their northernmost defeated came after they charged cavalry into an unbudging infantry square. Their main branch, which got a reputation for drunkenness, fell after Marwan II lost the Battle of Zab. This empire took power after the First Fitna, founded a branch emirate in Cordoba, and lost at Tours to Charles Martel. For 10 points, name this dynasty which built a royal mosque in Damascus, an early Islamic caliphate that fell to the Abbasids.
This empire's decline was hastened when frontier warriors at Merv rebelled.
Umayyad Caliphate [or Al-Ḫilāfa al-ʾumawiyya; or Banū ʾUmayya]