This project examines the institutional structure of power in the Achaemenid Persian Empire by focusing on the royal house and the Persian elite, particularly in their interactions with imperial borderlands. Moving beyond king-centered approaches, it conceptualizes power as embedded in institutions, with the royal house forming the core of a hierarchical system that operated through elite networks. The study situates these dynamics within the broader cultural context of interactions between (Indo-)Iranian, Elamite, and Ancient Near Eastern traditions. The research investigates whether members of the royal house and the Persian elite were key agents in shaping imperial strategies toward borderlands, both in expansion and in maintaining control. It draws on a wide range of multilingual sources, including royal inscriptions, administrative archives such as the Persepolis tablets, Babylonian and Aramaic records, and Greco-Roman accounts, and approaches them through institutional analysis. The project combines political history with socio-economic perspectives. It first reconstructs elite agency in frontier contexts, then examines administrative networks linking center and periphery, including the movement of people, goods, and tribute. By doing so, it aims to offer a new understanding of Achaemenid governance as a system of institutional power that enabled the empire to manage its diverse and extensive territories.