How did the Inca empire grow under Pachacuti and Topa Inca Yupanqui?

The rapid expansion of the Inca empire, often compared to the rise of Macedonia under Philip II and Alexander the Great, was primarily driven by Pachacuti Inca Yupanqui and his son Topa Inca Yupanqui between 1463 and 1493.12

Pachacuti Inca Yupanqui (1438–1471)

After securing his position in Cuzco, Pachacuti initiated a period of swift expansion. He defeated the Chanca and the Quechua, and organized military campaigns to conquer the Lake Titicaca Basin. He also sent expeditions northward to subdue territories as far as Quito, Ecuador, and brought the powerful Chimú kingdom under Inca control.324

Topa Inca Yupanqui (1471–1493)

Succeeding his father, Topa Inca Yupanqui continued this expansionist policy. He focused on:
* Southern Conquests: He conquered highland Bolivia, northern Chile, and northwestern Argentina, establishing the empire's southern boundary at the Maule River.524
* Consolidation: He incorporated the southern coast of Peru into the state and implemented administrative reforms, including labor taxation and population classification systems, to stabilize the vast new territories.54