From July to August 1764, Johnson negotiated a treaty at Fort Niagara. About 2,000 Native Americans were present, primarily Iroquois. Although most Iroquois had stayed out of the war, Senecas from the Genesee River valley had taken up arms against the British, and Johnson worked to bring them back into the Covenant Chain alliance. As restitution for the Devil's Hole ambush, the Senecas were compelled to cede the strategically important Niagara portage to the British. Johnson even convinced the Iroquois to send a war party against the Ohio Native Americans. This Iroquois expedition captured a number of Delawares and destroyed abandoned Delaware and Shawnee towns in the Susquehanna Valley, but otherwise the Iroquois did not contribute to the war effort as much as Johnson had desired.