The Iroquois began to conduct raids on the French settlements in 1640. In addition, Iroquois war parties became active along the St. Lawrence, attacking Huron canoes carrying furs to Quebec for trade with the French. They seized large shipments of furs, which they then traded to the Dutch at Fort Nassau (Albany, New York). The Iroquois exchanged the furs for weapons and ammunition. Their efforts to gain control of the fur trade led to a large-scale offensive against the Huron five years later.