Read this and answer the question. If the question is unanswerable, say "unanswerable".

The rivalries between the Arab tribes had caused unrest in the provinces outside Syria, most notably in the Second Muslim Civil War of 680–692 CE and the Berber Revolt of 740–743 CE. During the Second Civil War, leadership of the Umayyad clan shifted from the Sufyanid branch of the family to the Marwanid branch. As the constant campaigning exhausted the resources and manpower of the state, the Umayyads, weakened by the Third Muslim Civil War of 744–747 CE, were finally toppled by the Abbasid Revolution in 750 CE/132 AH. A branch of the family fled across North Africa to Al-Andalus, where they established the Caliphate of Córdoba, which lasted until 1031 before falling due to the Fitna of al-Ándalus.

What war strengthened the Umayyads?
unanswerable