Conversation so far:
who was the Inca ruler who greatly expanded the inca empire under his rule
with the arrival of the first great Inca leader Pachacuti Inca Yupanqui and the defeat of the Chanca in 1438 CE, the Incas began expanding south and in all directions.

Question: who was the successor
Self-contained rewrite: who was the successor to Pachacuti Inca Yupanqui.