Last updated

Scott's great snake, a cartoon map illustrating the Union blockade of the Confederacy during the American Civil War, known as the Anaconda Plan, illustrated by J.B. Elliott Scott-anaconda.jpg
Scott's great snake, a cartoon map illustrating the Union blockade of the Confederacy during the American Civil War, known as the Anaconda Plan, illustrated by J.B. Elliott
C47s unloading at Tempelhof Airport in Berlin, part of the airlift of supplies which broke the Soviet Union's 1948 land blockade of West Berlin C-47s at Tempelhof Airport Berlin 1948.jpg
C47s unloading at Tempelhof Airport in Berlin, part of the airlift of supplies which broke the Soviet Union's 1948 land blockade of West Berlin

A blockade is the act of actively preventing a country or region from receiving or sending out food, supplies, weapons, or communications, and sometimes people, by military force. A blockade differs from an embargo or sanctions, which are legal barriers to trade. It is also distinct from a siege in that a blockade is usually directed at an entire country or region, rather than a fortress or city and the objective may not always be to conquer the area.


While most blockades historically took place at sea, blockades are also used on land to prevent entrance of an area. For example, Armenia is a landlocked country that Turkey and Azerbaijan blockade. [1] Accordingly, Armenia cannot use these countries' air or land space for international trade, and Armenia mainly uses its northern borders to trade. As a result, the country's economy cannot function on a full scale and distracts the country's economic development. [2]

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 the blockade 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. Most recently, blockades have sometimes included cutting off electronic communications by jamming radio signals and severing undersea cables.


Although primitive naval blockades had been in use for millennia, the first successful attempts at establishing a full naval blockade were made by Admiral of the Fleet Edward Hawke during the Seven Years' War (1754–1763). [3] Following the British naval victory at Quiberon Bay, which ended any immediate threat of a major invasion of the British Isles, [4] the British implemented a tight economic blockade on the French coast. This began to starve French ports of commerce, further weakening France's economy. Hawke took command of the blockading fleet off Brest and extended the blockade of the French coast from Dunkirk to Marseilles. [5] The British were able to take advantage of the Navy's position to develop plans for amphibious landings on the coast. However, these plans were eventually abandoned, due to the formidable logistical challenge this would have posed. [6]

The strategic importance of the blockade was cemented during the Revolutionary and Napoleonic Wars, during which successful blockades on France were imposed by the Royal Navy, leading to major economic disruptions. The Union blockade of southern ports was a major factor in the American Civil War, as was the failure of the U-boat blockade in World War I and again in World War II.

Julian Corbett and Admiral Mahan emphasized that naval operations were chiefly to be won by decisive battles and blockade. [7]

Types of blockade

In World War II, German U-boats attempted to stop ships carrying food, supplies and materiel from reaching the United Kingdom, an example of a distant blockade. Uboatsafterthewar.jpg
In World War II, German U-boats attempted to stop ships carrying food, supplies and matériel from reaching the United Kingdom, an example of a distant blockade.

Close, distant, and loose blockades

A close blockade entails placing warships within sight of the blockaded coast or port, to ensure the immediate interception of any ship entering or leaving. It is both the most effective and the most difficult form of blockade to implement. Difficulties arise because the blockading ships must remain continuously at sea, exposed to storms and hardship, usually far from any support, and vulnerable to sudden attack from the blockaded side, whose ships may stay safe in harbor until they choose to come out.

In a distant blockade, the blockaders stay well away from the blockaded coast and try to intercept any ships going in or out. This may require more ships on station, but they can usually operate closer to their bases, and are at much less risk from enemy raids. This was almost impossible prior to the 16th century due to the nature of the ships used. [8]

A loose blockade is a close blockade where the blockading ships are withdrawn out of sight from the coast (behind the horizon) but no farther. The object of loose blockade is to lure the enemy into venturing out but to stay close enough to strike.

British admiral Horatio Nelson applied a loose blockade at Cádiz in 1805. The Franco-Spanish fleet under Pierre-Charles Villeneuve then came out, resulting in the Battle of Trafalgar. [9]

Pacific blockade

Until 1827, blockades, as part of economic warfare, were always a part of a war. This changed when France, Russia and Britain came to the aid of the Greek rebels against Turkey. They blockaded the Turkish-occupied coast, which led to the battle of Navarino. War was never declared, however, so it is considered the first pacific — i.e. peaceful — blockade. [10] The first truly pacific blockade, involving no shooting at all, was the British blockade of the Republic of New Granada in 1837, established to compel New Granada to release an imprisoned British consul. [11]

President Kennedy and his advisors discuss the Cuban Missile Crisis. Part of the US response to Soviet missiles being placed in Cuba was a naval blockade of the island. President Kennedy with advisors after EXCOMM meeting, 29 October 1962 crop.jpg
President Kennedy and his advisors discuss the Cuban Missile Crisis. Part of the US response to Soviet missiles being placed in Cuba was a naval blockade of the island.

Since 1945, the United Nations Security Council determines the legal status of blockades and by article 42 of the UN Charter, the council can also apply blockades. [12] The UN Charter allows for the right of self-defense but requires that this must be immediately reported to the Security Council to ensure the maintenance of international peace.

According to the not ratified document San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994, [13] a blockade is a legal method of warfare at sea but is governed by rules. The manual describes what can never be contraband. The blockading nation is free to select anything else as contraband in a list, which it must publish.

The blockading nation typically establishes a blockaded area of water, but any ship can be inspected as soon as it is established that it is attempting to break the blockade. This inspection can occur inside the blockaded area or in international waters, but never inside the territorial waters of a neutral nation. A neutral ship must obey a request to stop for inspection from the blockading nation. If the situation so demands, the blockading nation can request that the ship divert to a known place or harbour for inspection. If the ship does not stop, then the ship is subject to capture. If people aboard the ship resist capture, they can be lawfully attacked.

Act of war

Whether or not a blockade was seen as lawful depended on the laws of the nations whose trade was influenced by the blockade. The Brazilian blockade of Río de la Plata in 1826 during the Cisplatine War, for instance, was considered lawful according to British law but unlawful according to French and American law. The latter two countries announced they would actively defend their ships against Brazilian blockaders, while Britain was forced to steer for a peaceful solution between Brazil and Argentina. [14]

Civil disobedience

30,000 at Greenham Common. Embracing the base, Greenham Common December 1982 - - 759090.jpg
30,000 at Greenham Common.

There are a number of protest actions with the specific aim of cutting off material, people or communications from a particular area, either in part or totally. The effectiveness of such blockades rely on the participation of people and lock-on techniques.

A sit-down strike is a form of civil disobedience in which an organized group of workers, usually employed at a factory or other centralized location, take possession of the workplace by "sitting down" at their stations, effectively preventing their employers from replacing them with strikebreakers. A nonviolent picket is another example; it also illustrates the specificity of the blockade. Pickets may demand the blocking of some traffic while allowing other traffic; e.g. workers but not the customers, or customers but not workers.

The Mau movement was a nonviolent movement for Samoan independence from colonial rule during the early 1900s. Amongst other actions, participants formed their own "police force", picketing stores in Apia to prevent the payment of customs to the authorities. Some other examples are the perimeter blockade by human chain at Greenham Common Women's Peace Camp, the blockade of the Franklin River dam site, and the Keystone Pipeline.

Blockade planning

A Northern cartoonist ridicules the Union's initial attempts to blockade ports of the Confederacy in the American Civil War Blockade connecticut plan civil war cartoon.jpg
A Northern cartoonist ridicules the Union's initial attempts to blockade ports of the Confederacy in the American Civil War

Blockades depend on four general factors:

Blockade running

Blockade running is the practice of delivering cargo (food, for example) to a blockaded area. It has mainly been done by ships (called blockade runners) across ports under naval blockade. Blockade runners were typically the fastest ships available and often lightly armed and armored.

However, it is now also been done by aircraft, forming airbridges, such as over the Berlin blockade after World War II.

See also

Related Research Articles

Fourth Anglo-Dutch War UK–Netherlands war, 1780–1784

The Fourth Anglo-Dutch War was a conflict between the Kingdom of Great Britain and the Dutch Republic. The war, contemporary with the War of American Independence, broke out over British and Dutch disagreements on the legality and conduct of Dutch trade with Britain's enemies in that war.

Continental System 1806–1814 embargo of Napoleonic Europe against Britain

The Continental Blockade, or Continental System, was the foreign policy of Napoleon Bonaparte against the United Kingdom during the Napoleonic Wars. As a response to the naval blockade of the French coasts enacted by the British government on 16 May 1806, Napoleon issued the Berlin Decree on 21 November 1806, which brought into effect a large-scale embargo against British trade. The embargo was applied intermittently, ending on 11 April 1814 after Napoleon's first abdication. The blockade caused little economic damage to the UK, although British exports to the continent dropped from 55% to 25% between 1802 and 1806. As Napoleon realized that extensive trade was going through Spain and Russia, he invaded those two countries. His forces were tied down in Spain—in which the Spanish War of Independence was occurring simultaneously—and suffered severely in, and ultimately retreated from, Russia in 1812.

<i>Trent</i> Affair Diplomatic incident that almost brought the U.S. to war with the U.K. during the American Civil War

The Trent Affair was a diplomatic incident in 1861 during the American Civil War that threatened a war between the United States and the United Kingdom. The U.S. Navy captured two Confederate envoys from a British Royal Mail steamer; the British government protested vigorously. The United States ended the incident by releasing the envoys.

Swedish iron ore was an important economic factor in the European theatre of World War II. Both the Allies and the Axis were keen to gain control of the mining district in northernmost Sweden, surrounding the mining towns of Gällivare and Kiruna. The importance of this issue increased after other sources of iron were cut off from Germany by the Allied naval blockade during the Battle of the Atlantic. Both the planned Anglo-French support of Finland in the Winter War, and the following German occupation of Denmark and Norway during Operation Weserübung were to a large extent motivated by the wish to deny their respective enemies iron critical for wartime production of steel.

The London Declaration concerning the Laws of Naval War is an international code of maritime law, especially as it relates to wartime activities, proposed in 1909 at the London Naval Conference by the leading European naval powers, the United States and Japan, after a multinational conference that occurred in 1908 in London. The declaration largely reiterated existing law, but dealt with many controversial points, including blockades, contraband and prize, and showed greater regard to the rights of neutral entities.

A pacific blockade is a blockade exercised by a great power for the purpose of bringing pressure to bear on a weaker state without actual war. It can be employed only as a measure of coercion by maritime powers able to bring into action such vastly superior forces to those the resisting state can dispose of that resistance is out of the question. The term was created by Laurent-Basile Hautefeuille, a French writer on international maritime law.

Operation Wilfred was a British naval operation during the Second World War that involved the mining of the channel between Norway and its offshore islands to prevent the transport of Swedish iron ore through neutral Norwegian waters to be used to sustain the German war effort. The Allies assumed that Wilfred would provoke a German response in Norway and prepared a separate operation known as Plan R 4 to occupy Narvik and other important locations.

Union blockade Union blockade of the Confederacy in the U.S. Civil War

The Union blockade in the American Civil War was a naval strategy by the United States to prevent the Confederacy from trading.

Command of the sea Complete control of naval warfare

Command of the sea is a naval military concept regarding the strength of a particular navy to a specific naval area it controls. A navy has command of the sea when it is so strong that its rivals cannot attack it directly. This dominance may apply to its surrounding waters or may extend far into the oceans, meaning the country has a blue-water navy. It is the naval equivalent of air supremacy.

Naval strategy is the planning and conduct of war at sea, the naval equivalent of military strategy on land.

Prize (law) Vessel, cargo, or equipment captured during armed conflict on the seas

Prize is a term used in admiralty law to refer to equipment, vehicles, vessels, and cargo captured during armed conflict. The most common use of prize in this sense is the capture of an enemy ship and her cargo as a prize of war. In the past, the capturing force would commonly be allotted a share of the worth of the captured prize. Nations often granted letters of marque that would entitle private parties to capture enemy property, usually ships. Once the ship was secured on friendly territory, she would be made the subject of a prize case, an in rem proceeding in which the court determined the status of the condemned property and the manner in which the property was to be disposed of.

USS <i>Daylight</i> (1859)

The USS Daylight was a steamship acquired by the Union Navy during the American Civil War. She was used by the Navy to patrol navigable waterways of the Confederacy to prevent the South from trading with other countries.

The Confederate privateers were privately owned ships that were authorized by the government of the Confederate States of America to attack the shipping of the United States. Although the appeal was to profit by capturing merchant vessels and seizing their cargoes, the government was most interested in diverting the efforts of the Union Navy away from the blockade of Southern ports, and perhaps to encourage European intervention in the conflict.

First League of Armed Neutrality European Naval Alliance (1780-1783)

The first League of Armed Neutrality was an alliance of European naval powers between 1780 and 1783 which was intended to protect neutral shipping against the Royal Navy's wartime policy of unlimited search of neutral shipping for French contraband during the American Revolutionary War and Anglo-French War. British naval commanders followed their instructions with care, ordered away boarding parties and made seizures with impunity. According to one estimate, 1 in 5 merchant vessels did not make it to port safely due to this policy. By September 1778, at least 59 ships were taken prize - 8 Danish, 16 Swedish and 35 Dutch, not mentioning others from Prussia. Protests were enormous by every side involved.

Affair of Fielding and Bylandt

The affair of Fielding and Bylandt was a brief naval engagement off the Isle of Wight on 31 December 1779 between a Royal Navy squadron, commanded by Commodore Charles Fielding, and a naval squadron of the Dutch Republic, commanded by rear-admiral Lodewijk van Bylandt, escorting a Dutch convoy. The Dutch and British were not yet at war, but the British wished to inspect the Dutch merchantmen for what they considered contraband destined for France, then engaged in the American War of Independence.

Many legal assessments of the Gaza flotilla raid were published subsequent to the event. International law experts differed over the legality of the action by Israel. Most agree that Israel is entitled to impose and enforce a naval blockade, that Israel can intercept a ship in international waters headed for a belligerent territory, that Israel may use force when intercepting such ships, and that there must be a proportional relationship between the threat and response. The force necessary to respond to violent resistance and whether the force that was used was proportionate were disputed.

The San Remo Manual on International Law Applicable to Armed Conflicts at Sea was adopted in June 1994 by the International Institute of Humanitarian Law after a series of round table discussions held between 1988 and 1994 by diplomats and naval and legal experts. It is "the only comprehensive international instrument that has been drafted on the law of naval warfare since 1913."

Victoria Affair

The Victoria Affair was a military operation conducted by the Israel Defense Forces (IDF) in March 2011 in which the Israeli Navy intercepted the vessel Victoria on the international waters in the Mediterranean, and discovered concealed weapons which, according to the IDF, were destined for Palestinian militant organizations in the Gaza Strip. The vessel was found to be carrying approximately 50 tons of weapons, including C-704 anti-ship missiles, rocket launchers, radar systems, mortar shells and rifle ammunition.

Blockade of Germany (1939–1945) British and French operation to restrict German and Italian supply lines during WWII

The Blockade of Germany (1939–1945), also known as the Economic War, was carried out during World War II by the United Kingdom and France in order to restrict the supplies of minerals, metals, food and textiles needed by Nazi Germany – and later Fascist Italy – in order to sustain their war efforts. The economic war consisted mainly of a naval blockade, which formed part of the wider Battle of the Atlantic, and included the preclusive buying of war materials from neutral countries to prevent their sale to the enemy.

Eastern Fleet (India) Military unit

The Eastern Fleet is a Naval fleet of the Indian Navy. It is known as the 'Sword Arm' of the Eastern Naval Command and called the Sunrise Fleet. It is headquartered at Visakhapatnam, Andhra Pradesh on the east coast of India. It is a part of the Eastern Naval Command and is responsible for the naval forces in the Bay of Bengal and parts of the Indian Ocean.


  1. "Opening Borders: Armenia's Economic Risks". Retrieved 12 May 2021.
  2. Sahakyan, Armen (20 February 2014). "Economic Blockades and International Law: The Case of Armenia". The Armenian Weekly. Retrieved 12 May 2021.
  3. Richard Harding (2002). Seapower and Naval Warfare, 1650–1830. Routledge. Retrieved 7 February 2013.
  4. Anderson p.381-83
  5. Corbett p.86
  6. Corbett p.93-94
  7. Vego, Dr. Milan (2009). "Naval Classical Thinkers and Operational Art". Naval War College: 4. Archived from the original on 31 January 2017. Retrieved 12 December 2016.Cite journal requires |journal= (help)
  8. Palmer, Michael A., Command at Sea: Naval Command and Control since the Sixteenth Century, Harvard University Press, Cambridge, 2005, p.22
  9. Reynolds, Clark G. 1998. "Navies in History", p. 98. ISBN   1-55750-715-5.
  10. Oppenheim, L. & Roxburgh, Ronald. 2005. "International Law: A Treatise", p. 53. ISBN   1-58477-609-9.
  11. Encyclopædia Britannica, 11th edition. 1911. "Pacific Blockade", vol. 20, p. 433-434.
  12. D'Amato, Anthony A. 1995. "International Law and Political Reality: Collected Papers", p. 138. ISBN   90-411-0036-9.
  13. San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994.
  14. Sondhaus, Lawrence. 2004. "Navies in Modern World History", p. 98. ISBN   1-86189-202-0.