In military operations, reconnaissance is the exploration outside an area occupied by friendly forces to gain information about natural features and enemy presence. Examples of reconnaissance include patrolling by troops (Long Range Reconnaissance Patrol, U.S. Army Rangers, scouts, or military intelligence specialists), ships or submarines, manned/unmanned reconnaissance aircraft, satellites, or by setting up covert observation posts. Espionage normally is not reconnaissance, because reconnaissance is a military's special forces operating ahead of its main forces; spies are non-combatants operating behind enemy lines.