Final answer:
Civil war critically weakened the Songhai Empire after Askia the Great's reign, leading to political chaos, weakened administration, and making the empire vulnerable to external conquests.
Step-by-step explanation:
The impact of civil war on the Songhai Empire after Askia the Great's reign was substantial and destructive. Following the aging of Askia the Great, the empire experienced a period of internal conflict after 1528 when his sons revolted and ousted him, and one brother, Musa, was proclaimed king. This succession did not go unchallenged, which led to further civil war and the eventual killing of Musa by his brothers in 1531. Such conflicts sharply weakened the empire by disrupting the administration and causing political chaos. External groups started to see opportunities to intervene, hoping to seize control of the profitable trans-Saharan trade in salt and gold.
During Askia the Great's rule, the Songhai Empire had reached the peak of its power, controlling access to major trade routes across the Sahara and regulating trade with the introduction of standardized weights and measures. However, after his death, the subsequent leaders were unable to maintain control and oversee the once thriving empire. The introduction of successive, ineffective rulers plunged the empire into further decline and laid it open to external conquest, such as the invasion by the Saadi forces from Morocco to gain control of the trans-Saharan caravan routes. Therefore, civil war critically weakened the Songhai Empire following the reign of Askia the Great.