Final answer:
Huayna Capac died from smallpox, and a civil war ensued between his sons Huascar and Atahualpa for succession of the Inca Empire.
Step-by-step explanation:
Huayna Capac died from smallpox. His sons Huascar and Atahualpa fought over who would become the next leader of the Inca Empire. This brutal civil war occurred right before the arrival of the Spanish conquistadors led by Francisco Pizarro, which greatly weakened the empire and contributed to its downfall.
The war between Huascar and Atahualpa was a significant event, with Atahualpa eventually emerging victorious, although his reign was short-lived as he was soon after captured and killed by the Spaniards in 1533.