5-4. The responsibility for accomplishing reconnaissance does not reside solely with reconnaissance units. Every unit has an implied mission to report information about the terrain, civilian activities, and friendly and enemy dispositions. Troops in contact with an enemy and reconnaissance patrols of maneuver units, at all echelons, collect information on enemy units and activities. In echelon support and consolidation areas, reserve maneuver forces, functional and multifunctional support and sustainment elements, other governmental agencies, and multinational forces observe and report civilian, adversary, and enemy activity and significant changes in terrain trafficability. Although all units conduct reconnaissance, ground cavalry, aviation attack reconnaissance units, scouts, and special forces are specifically trained to conduct reconnaissance operations. Some branches, such as the Corps of Engineers and Chemical Corps, conduct specific reconnaissance operations that complement the force’s overall reconnaissance effort. However, BCT, division, and corps commanders primarily use their organic or attached reconnaissance—ground or air—and intelligence elements to accomplish reconnaissance.