Under the leadership of Manco Cápac, the Inca formed the small city-state Kingdom of Cusco (Quechua Qusqu’, Qosqo). In 1438, they began a far-reaching expansion under the command of Sapa Inca (paramount leader) Pachacuti-Cusi Yupanqui, whose name meant “earth-shaker.” The name of Pachacuti was given to him after he conquered the Tribe of Chancas (modern Apurímac). During his reign, he and his son Tupac Yupanqui brought much of the modern-day territory of Peru under Inca control.
Source: Wikipedia