Answer
Civil war marked al-Ma'mun's rise to power. After the death of his father, Harun al-Rashid, in 809, a power struggle ensued between al-Ma'mun and his older brother, al-Amin. The conflict escalated into a full-scale civil war, with al-Ma'mun emerging victorious in 813. This victory solidified his position as the caliph and marked the beginning of his reign.