The Chanca (or Chanka) tribe, a “powerful warlike confederation” (McEwan), attacks the city of Cusco as it attempts an aggressive expansion to the south. Pachacuti led the military defense against the Chanka while his father and his brother, Urco Inca, fled the manor. The victory over the Chankas made Inca Viracocha recognize him as his successor around 1438. He conquered the provinces of Colla-Suyu and Chinchay-Suyu. Along with his sons, Tupac Ayar Manco (or Amaru Tupac Inca), and Apu Paucar Usnu, he defeated the Collas. Additionally, he left garrisons in subjugated lands. Pachacuti rebuilt much of Cusco, designing it to serve the needs of an imperial city and as a representation of the empire. Most archaeologists now believe that the famous Inca site of Machu Picchu was built as an estate for Pachacuti.