The Incas civilization arose around 1438 in present-day Peru. Led by the ruler Pachacuti, the Incas expanded their territory through military campaigns and alliances to become a large empire. They developed impressive architecture, roads, and agricultural systems without the use of wheels or writing. Inca society was organized hierarchically with the Sapa Inca as ruler. Disease brought by Europeans in the 1500s and a civil war between two rulers weakened the empire, allowing the Spanish conquistadors to eventually take control of the region in 1532.