Complex sentence: During the war, the Seven Nations of Canada were allied with the French; they were Native Canadian groups living in the Laurentian valley--the Algonquin, the Abenaki, the Huron and others.
Split into simpler sentences: During the war, the Seven Nations of Canada were allied with the French. These were Native Canadian groups living in the Laurentian valley--the Algonquin, the Abenaki, the Huron and others.