Legal action by a government or group of governments restricting the departure of vessels or movement of goods from some or all locations to one or more countries. A trade embargo is a prohibition on exports to one or more countries. A strategic embargo restricts only the sale of goods that make a direct and specific contribution to a country's military power; similarly, an oil embargo prohibits only the export of oil. Broad embargoes often allow the export of certain goods (e.g., medicines or foodstuffs) to continue for humanitarian purposes, and most multilateral embargoes include escape clauses that specify a limited set of conditions under which exporters may be exempt from their prohibitions. An embargo is a tool of economic warfare that may be employed for a variety of political purposes, including demonstrating resolve, sending a political signal, retaliating for another country's actions, compelling a country to change its behaviour, deterring it from engaging in undesired activities, and weakening its military capability.