Under the leadership of Sorley Boy MacDonnell, Clan Ian Mor became a major force in the development of the Gaelic heartland - the Western Highlands, the Isles of Scotland and Ulster. He was able to hold together Clan Ian Mor as an effective political and military force in the Celtic fringe. This volume is an important contribution to our understanding of the War of the Three Kingdoms and the political and territorial shaping of the British Isles in the seventeenth century.