This interval witnessed drastic changes in political formations throughout Southeast Mesoamerica. These shifts generally took the form of political decentralization as what had been regional capitals were largely abandoned and replaced by the more muted expressions of political preeminence that took shape in smaller, dispersed political centers. A major exception to this trend is found at the site of Copán. The arrival here of interlopers from the Maya lowlands, led by K’inich Yax K’uk’ Mo’, transformed this settlement into the capital of a realm ruled according to principles previously foreign to the Southeast but which were well established among lowland Maya domains to the west. Much of the chapter is devoted to exploring how this singular event was possibly implicated in changes occurring elsewhere in Southeast Mesoamerica at this time. Copán’s rulers, outside their realm, did not determine the course of any area’s local history. Their mode of rule that combined political centralization with marked expressions of hierarchy, however, offered a model that their Southeastern neighbors could and did adapt to their own purposes.