There are a number of protest actions with the specific aim of partially or completely cutting off equipment, people or communications from a particular area. The effectiveness of these blockades depends on human intervention and locking techniques. The tight patrol of enemy ports to prevent naval forces from taking to the sea is also known as blockade. When coastal cities or fortresses were besieged on the land side, besiegers often blocked the sea side. More recently, blockages have sometimes involved cutting off electronic communications by jamming radio signals and cutting submarine cables. In a memorandum prepared for the London Naval Conference of 1908-09, the British government defined a blockade as “an act of war perpetrated by warships of a belligerent to prevent access to or departure from a defined part of the enemy coast.” This differs from a so-called blockade of the Pacific in that the latter is not strictly speaking a war operation and cannot be legally enforced against neutrals. The first can be military or commercial. A military blockade is carried out to achieve a specific military objective, such as the capture of a naval port. A commercial blockade has no immediate military objective, but aims to induce the enemy to surrender or reconcile by cutting off all trade by sea. A belligerent may, if he can, block the entire coast of the enemy, but the mere proclamation of a blockade of all or part of the enemy`s coast, without anything more, has no legal effect. Such proclamations were common and were called “paper blockades.” A belligerent shall not block neutral territory unless it is effectively under the control or occupation of the enemy, nor shall it block enemy territory in a manner that prevents access to neutral territory. A blockade is an act of war governed by international law, namely the 1856 Paris Declaration on the Law of the Sea and Articles 1 to 22 of the 1909 London Declaration on the Law of Naval War. It is important to distinguish between the terms blockade and embargo.

An embargo is a type of economic sanction that can be imposed under the auspices of the United Nations or another international organization to force a state to comply with a decision. The reprisals also served as the basis for the British decree of 11 March 1915, according to which neutral ships carrying goods suspected of being of enemy destination, property or origin were to be brought into port, unloaded and detained for the duration of the war. On January 31, 1917, Germany and Austria-Hungary announced a policy of unrestricted submarine warfare in certain areas, which Germany again sought to justify in order to counter “the illegal measures of its enemies”. Britain responded with a settlement in the Council of 16. February 1917, which declared that any ship found at sea en route to or from a port of a neutral country giving access to enemy territory without first calling at a British or allied port should be deemed to be carrying goods of enemy property or origin until proven otherwise. A blockade ends (1) when it is explicitly imposed by the blocking government or the commander of the blockade force, (2) when it is no longer effectively maintained, or (3) when the blocked place is effectively occupied by the blocking state. The penalty for violation of the blockade was in any event the loss of the vessel and cargo, if the blockade was known at the time of shipment or could have been known to the consignor. The most important case of a formal blockade of World War II occurred with the announcement of a blockade of the Finnish coast and adjacent islands by the Soviet Union in December 1939. Finland questioned the Soviet Union`s right, as a participant in the war, to establish the blockade, as Russia had previously denied the existence of a state of war with Finland.

The effectiveness of the blockade was also questioned. However, the issues raised in this way were not resolved until the end of the war. The tactical disadvantage faced by a belligerent is not historically a new geographical situation. In the Napoleonic Wars, the transport of water by river and canal through Baltic Sea ports was as essential to supplying France as the “network of railways and waterways” that supplied Germany during the First World War. Nevertheless, the manner in which naval blockades were enforced and the effectiveness of the blockade of naval operations had changed greatly because of the conditions of war. The greater range of coastal batteries, the use of torpedo boats and similar boats, the action of submarines and mines, and the use of aircraft for bombing raids and surface machine-gun vehicles had made tight blockade or blockade by stationary ships impossible. The blocking squadron was now forced to operate some distance from the enemy coast. On the other hand, the effectiveness of the blocking forces was increased by the ability of the modern warship to be independent of the elements; communicate by radio with other ships in the squadron and with the command; work at high speed; use radar, war aircraft and submarines for reconnaissance purposes; and radar and searchlights for night operations. Although primitive naval blockades were used for millennia, the first successful attempts to establish a full naval blockade were made by the British Royal Navy during the Seven Years` War (1754–1763) against the France. [3] After the victory of the British Navy in Quiberon Bay, which ended any imminent threat of a major invasion of Britain,[4] Britain established a strict blockade on the French coast.

This starved French commercial ports and weakened the French economy. Admiral Edward Hawke took command of the blockade fleet off Brest and extended the blockade to the entire French Atlantic coast from Dunkirk to Bordeaux and also to Marseille on the French Mediterranean coast. [5] One of the most important blockades of the post-war period took place not on water, but on land. The city of Berlin, divided into eastern and western zones, was blockaded by the Soviet Union from June 1948 to May 1949.