Around 900 AD, when - for reasons still unclear - the Classic Maya culture began to crumble, these cities were abandoned. During the early Postclassic period (900-1200 AD), waves of Nahuat-speaking groups began to migrate south from Mexico, seeking land and power. These settlers, who established themselves in west and central El Salvador and in the northwest around MetapA?n, came to be known as the Pipils . New seats of power were built at CihuatA?n, TehuacA?n and CuscatlA?n; unusually, the deserted Maya city of Tazumal was also reoccupied. The new settlers planted maize, beans, cocoa and tobacco, lived in highly stratified societies under a hereditary system of military rule, had highly developed arts and sciences and worshipped the sun and the idols of Quetzalcoatl (man), Itzqueye (woman), Tlaloc (rain) and Mictlanteuctli (god of the underworld). Trade links with the west and north were strong, based on the exchange of cocoa, which was extensively cultivated.

Final waves of Nahuat speakers arrived in the thirteenth and fourteenth centuries, threatening and occasionally displacing the already established communities and disrupting the network of trade, possibly contributing to the abandonment of CihuatA?n and TehuacA?n. Chief among the new immigrants were the Nonualcos , who settled around what is now the city of Zacatecoluca, and the Pok'omans who moved in around Chalchuapa.