Throughout his decades-long career, Weiser built on his knowledge of Native American languages and culture to become a key player in treaty negotiations, land purchases, and the formulation of Pennsylvania's policies toward Native Americans. Because of his early experiences with the Iroquois, Weiser was inclined to be sympathetic to their interpretation of events, as opposed to the Lenape or the Shawnee. This may have exacerbated Pennsylvanian-Lenape/Shawnee relations. Their alliance with the French during the war resulted in deaths of Pennsylvania colonists during the French and Indian Wars.