In a series of Indian treaties Harrison opened a huge area for settlement. The Delaware, Miami, Potawatomi, and Eel Indians ceded approximately three million acres in return for annuities ranging from $200 to $1,000 to each tribe. With continuing settlement Indian hostility grew. In 1809 the threat against settlers became serious. The northwestern tribes, encouraged by the British, rallied behind Shawnee warriors Tecumseh and his brother, the Prophet. A confrontation between Harrison and the brothers, at Grouseland in August 1810, failed to reconcile conflicting Indian and American interests.