Complex sentence: RAC employees began constructing on the Stikine Strait a fort named the Redoubt Saint Dionysius or the Redoubt San Dionisio, usually thought to have been located on Zarembo Island, to ensure control of the local fur trade, critical to the economic basis of New Archangel.
Split into simpler sentences: RAC employees began constructing on the Stikine Strait a fort named the Redoubt Saint Dionysius or the Redoubt San Dionisio, usually thought to be located on Zarembo Island. Ensure control of the local fur trade, critical to the economic basis of New Archangel.