Throughout this decades-long career, Weiser's knowledge of Native American languages and culture made him a key player in treaty negotiations, land purchases, and the formulation of Pennsylvania's policies towards 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, with bloody consequences in the French and Indian Wars. Nevertheless, for many years, he helped to keep the powerful Iroquois, or Six Nations, allied with the British as opposed to the French. This important service contributed to the continued survival of the British colonies and the eventual victory of the British over the French in the French and Indian Wars.