封鎖

A blockade is the use of military force to prevent food, supplies, weapons, or communications, and sometimes people, entering or leaving a country or region.Unlike sanctions or an embargo, which are legal barriers to trade, a blockade is physical. Blockades are distinct from sieges in that a blockade is usually directed at an entire country or region, rather than a fortress or city, and the objective of a blockade is not necessarily to conquer the area.A blockading power can seek to cut off all maritime transport from and to the blockaded country, although stopping all land transport to and from an area may also be considered a blockade. Blockades restrict the trading rights of neutrals, who must submit for inspection for contraband, which the blockading power may define narrowly or broadly, sometimes including food and medicine. In the 20th century, air power has also been used to enhance the effectiveness of blockades by halting air traffic within the blockaded airspace.Close patrol of hostile ports, in order to prevent naval forces from putting to sea, is also referred to as a blockade. When coastal cities or fortresses were besieged from the landward side, the besiegers would often blockade the seaward side as well. Modern blockades have included cutting off electronic communications by jamming radio signals and severing undersea cables. Blockades often result in the starvation of the civilian population, notably during the blockade of Germany during World War I and the blockade of Biafra during the Nigerian Civil War.