At first it looked like the British were on the Chickasaw's side. The Royal Proclamation of 1763 recognized the rights of Native Americans to own land — changing the legal relationship between settlers and the Native Americans. The proclamation made it very clear that the land west of the Appalachians was for "Indians, and persons who had already settled there were to leave."
Britain promised this land to the Native Americans to gain their support during the French and Indian War (also known as the Seven Years' War). Britain had massive war debts and did not want to pay to protect settlers in the West. This treaty was meant to regulate future expansion and keep Native American relations firmly in control of the British government through the office of the Indian Department.