A less appreciated aspect of Forbes' leadership was in building relationships with local Native Americans, who previously refused to co-operate with the British. These efforts were bolstered by the capture of Fort Frontenac in August, increasing British prestige, while the loss of French traders severely impacted the local economy. This methodical approach was jeopardised by the Battle of Fort Duquesne, on 15 September 1758, when a column under Major James Grant advanced too far ahead of the main body and suffered over 300 casualties. Forbes decided to suspend operations but on 26 October, 13 Ohio Valley tribes signed the Treaty of Easton with Pennsylvania and New Jersey.