The Middle Horizon period (ca. AD 600–1000) in the Central Andes marked an era of sociopolitical expansion and cultural transformation, characterized by the rise of two major highland polities: Wari, based in the central highlands of Ayacucho, and Tiwanaku, centered around the southern Lake Titicaca Basin. The Moquegua Valley in southern Peru represents a rare and archaeologically rich context in which both states established colonies, making it an ideal setting to explore frontier dynamics, interregional interaction, and statecraft beyond core territories. This talk examines the nature of Wari and Tiwanaku presence in the Moquegua Valley through a multidisciplinary synthesis of archaeological, architectural, ceramic, and environmental data. While Tiwanaku established large-scale agrarian settlements such as Chen Chen and Omo in the middle valley, characterized by altiplano-style domestic and ceremonial architecture, Wari constructed an administrative and ritual complex at Cerro Baúl in the upper valley, supported by intensive terrace irrigation and monumental public buildings. The coexistence of these polities for over three centuries within the same ecological corridor raises important questions about conflict, cooperation, and competition in frontier zones. Through analysis of material culture—including ceramic production and distribution, architectural forms, and ritual paraphernalia—this talk explores the ways in which each state articulated political identity and negotiated local resources. Recent isotopic and compositional studies reveal that both groups mobilized distinct local resources while maintaining ties to their highland homelands. Additionally, this talk evaluates the role of environmental stressors, particularly shifting climate patterns and water scarcity, in shaping the trajectory of Wari–Tiwanaku relations and their eventual decline in the region.