The history of Scotland's most famous clans. There can be few Highland Clans more mired in bloodshed than Clan Campbell. The Campbells combined an understanding of the law with formidable might to become the most powerful and influential clan in the country. But in the middle of the 17th century Scotland was ravaged by a bloody civil war that gave the Campbell's bitter rivals, the MacDonalds an opportunity to exact revenge. Thousands died as these two mighty Highland Clans battled for supremacy.