A blockade is a strategy used to prevent goods, services, or people from entering or leaving a specific area. This can be done by military forces, ships, or other means to restrict access, often during conflicts or wars. The goal is to weaken an opponent by cutting off their supplies and resources. Blockades can be implemented on land or at sea, affecting trade and communication. Historical examples include the Union blockade during the American Civil War and the Berlin Blockade in 1948-1949. These actions can lead to significant economic and humanitarian impacts on the affected population.