In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmishers, long-range reconnaissance patrol, U.S. Army Rangers, cavalry scouts, or military intelligence specialists), ships or submarines, manned or unmanned reconnaissance aircraft, satellites, or by setting up observation posts. Espionage is usually considered to be different from reconnaissance, as it is performed by non-uniformed personnel operating behind enemy lines.