Raiding, also known as depredation, is a military tactic or operational warfare mission which has a specific purpose. Raiders do not capture and hold a location, but quickly retreat to a previous defended position before enemy forces can respond in a coordinated manner or formulate a counter-attack. A raiding group may consist of combatants specially trained in this tactic, such as commandos, or as a special mission assigned to any regular troops. Raids are often a standard tactic in irregular warfare, employed by warriors, guerrilla fighters or other irregular military forces. Some raids are large, for example the Sullivan Expedition.