The later part of the Bronze Age (1500-700 BC) was a time of settlement expansion and economic prosperity in Ireland. This was a landscape of small autonomous farming communities, but there is also evidence for control of territory and population, involving centralized organization of trade and economy, ritual and military force. That concentration of power was connected to the emergence of chiefdom polities active in the consolidation of large regional territories. Their competitive tendencies led on occasion to conflict and warfare, at a time of growing militarism evident in the mass production of bronze weaponry, including the first use of swords. Hillforts are another manifestation of a warrior culture that emerged not only in Ireland but across Europe during the Middle and Late Bronze Age. They were centers for high-status residence, ceremony and assembly, and represented an important visual display of power in the landscape. This is the first project to study hillforts in relation to warfare and conflict in Bronze Age Ireland. New evidence for the destruction of hillforts is connected to territorial disputes and other forms of competition arising from the ambitions of regional warlords, often with catastrophic consequences for individual communities. This project combines remote sensing and GIS-based landscape analysis with conventional archaeological survey and excavation, to investigate ten prehistoric hillforts across southern Ireland. These include a cluster of nine examples at Baltinglass, Co. Wicklow, often termed 'Ireland's hillfort capital'. The results provide new insights into the design and construction of these immense sites, as well as details of their occupation and abandonment. The chronology of Irish hillforts is reviewed, with a new understanding of origins and development. The project provides a challenging insight into the relationship of hillforts to warfare, social complexity and the political climate of late prehistoric Ireland.