 Clark, the preeminent American military leader on the northwestern frontier, worked with Governor Thomas Jefferson of Virginia in planning an expedition to capture Detroit, by which they hoped to bring an end to British support of the Indian war effort.In early August 1781, Clark and about 400 men left Fort Pitt in Pennsylvania by boat, floating down the Ohio River a few days ahead of Lochry and his men, who were trying to catch up.Joseph Brant's force was part of a combined British and Indian army being raised to counter Clark's offensive.