Complex sentence: By the time of the arrival of the French in 1720, the Mississaugas were already a distinct tribe of Anishinaabe people that moved from the Mississagi River area southward into Wendat territories on the Bruce Peninsula and eastward about Kawartha lakes.
Split into simpler sentences: By the time the French explorers arrived in 1720, the Mississaugas were a distinct tribe of Anishinaabe people. They had moved from the Mississagi River area southward into Wendat territories on the Bruce Peninsula and eastward about the Kawartha lakes.