Answer
Yazid I, the son of Mu'awiya I, faced opposition from Ibn al-Zubayr, who claimed the caliphate for himself. Ibn al-Zubayr refused to recognize Yazid's legitimacy due to his lavish lifestyle, which he saw as unfitting for a Muslim leader. This disagreement marked the beginning of the Second Fitna, a civil war within the Umayyad dynasty that lasted several years.