British forces in the American west used the settlement of Detroit as the base of operations to deal with Indians and encourage them to attack frontier settlements. Problems were especially severe in the Kentucky area, where Lieutenant Colonel George Rogers Clark was assigned the task of finding a military solution. In 1778, Clark and his men attempted to go to the source of the problem by seizing the settlements of Kaskaskia and Vincennes in the Illinois country. Vincennes was retaken by the British, who lost it again to Clark in 1779. Despite that defeat, Loyalists and Indians continued raids in the West until the end of the war, inflicting especially heavy losses in the Wyoming and Cherry valleys of Pennsylvania.