A military tactic through which ports are shut off to keep people and or supplies from moving in or out is called a blockade. A blockade is usually directed at an entire country or region and is different from a siege which targets a fortress or a city. It is also distinct from an embargo or sanctions, which are actually legal barriers to trade.
While most blockades in history took place at sea , blockades were also used on land to prevent someone from coming into a certain area. In the 20th Century, air power has also been used to enhance the effectiveness of the blockade by halting air traffic within the blockaded airspace.