After the collapse of the pre-classic Mayan civilization, a period of around two centuries elapsed before their re-emergence. There is evidence of political interference from Teotihuacan, the powerful Mexican city-state at this time: possibly it acted as a cultural or commercial catalyst. By 600 CE, a vibrant, prosperous, competitive network of city-states connected the Gulf, Caribbean and Pacific. They were governed by shifting alliances, with frequent double-dealing and violence. Perhaps the most powerful cities were Tikal and Calakmul, both heading confederacies. From the 8th century, the ruling dynasties were abruptly obliterated, one by one: the reason why is unclear. The Mayan revival in the 10th century evinced reduced circumstances. The epicentre was now in Yucatan, the culture more secular – perhaps the gods had been discredited – with Chichen Itza and Mayapan vying for supremacy. Another cluster recovered in the Guatemalan highlands. By the Spanish arrival in 1517, even these cities had fallen into disuse or decline.