Forward air control is the provision of guidance to Close Air Support (CAS) aircraft intended to ensure that their attack hits the intended target and does not injure friendly troops. This task is carried out by a forward air controller (FAC). The rugged jungle terrain of South East Asia readily hid enemy troop movements. U.S. fighter-bombers were so fast that pilots had great difficulty in distinguishing between enemy troops, friendly troops, and civilians. Forward air controllers directing air strikes thus became essential in usage of air power.