Blockade
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A blockade is the act of actively preventing a country or region from receiving or sending out
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,
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. 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.[1]
According to modern international law, blockades are an act of war.
History
Although primitive naval blockades have been in use for millennia, early attempts were limited by the time ships were able to stay at sea uninterruptedly.[7] The first successful attempts at establishing a full naval blockade were made by the British Royal Navy during the Seven Years' War (1754–1763) against France.[8] Following the 1759 British naval victory at Quiberon Bay, which ended any immediate threat of a major invasion of Britain,[9] the British Royal Navy established a close blockade on the French coast. This starved French ports of commerce, weakening France's economy. Admiral Edward Hawke took command of the blockading fleet off Brest and extended the blockade to cover the entire French Atlantic coast from Dunkirk to Bordeaux, and also to Marseille on France's Mediterranean coast.[10] During the North American operations of the Seven Years' War, the British Royal Navy also blockaded the French on the other side of the Atlantic, specifically impeding access and supply to the colonies of New France on the St. Lawrence.[11] Blockades thus contributed to the French loss of Canada in 1763.[12]
The strategic importance of blockade became increasingly apparent during the
Naval strategic thinkers, such as Sir Julian Corbett (1854-1922) and Alfred Thayer Mahan (1840-1914), wrote that naval conflicts were won primarily by decisive battles, but also by blockade.[13]
Types of 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.[14]
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
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.[16] 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.[17]
Legal status

Since 1945, the
According to the not ratified document San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994,[19] 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
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.[20]
Blockade planning
Blockades depend on four general factors

- The value of the item being blockaded must warrant the need to blockade. For example, during the 1962 Cuban Missile Crisis, the items to be blockaded (or "quarantined" to use the more neutral term selected by President John F. Kennedy) were Medium-range ballistic missiles, capable of delivering nuclear weaponry, bound for Cuba. Their value was high, as a military threat against the United States.
- The strength of the blockading force must be equal to or greater in strength than the opposition. The blockade is only successful if the 'thing' in question is prevented from reaching its receiver. For example, the overwhelming power of the Royal Navy allowed a successful blockade of Germany during and after World War I.
- Geography. Knowing the routes of the enemy will help the blockader choose where to blockade: for example, a high mountain pass or a strait is a natural choke point and a candidate for fortification.
- A blockade tends to be a long campaign requiring a long-term commitment by the blockading power. The Atlantic U-boat campaign of World War I and Battle of the Atlantic were essentially about German blockades, and lasted nearly as long as their respective wars. The Imperial Japanese Navy, however, made only sporadic efforts at blockade during the Pacific War, preferring to seek victory by fleet action.
Blockade running
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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. It is now also been done by aircraft, forming airbridges, such as over the Berlin Blockade after World War II.
See also
- Blockade of the Gaza Strip
- Blockade of Nagorno-Karabakh
- Command of the sea
- List of blockades
- Maritime Exclusion Zone
- No-fly zone
- Sea lines of communication
- Navicert
References
- ^ Nicholas Mulder, Boyd van Dijk (2021). "Why Did Starvation Not Become the Paradigmatic War Crime in International Law?". Contingency in International Law: On the Possibility of Different Legal Histories. Oxford University Press. pp. 370–.
- JSTOR 48714684.
- ^ Dannenbaum, Tom (28 July 2023). "What You Need to Know: International Humanitarian Law and Russia's Termination of the Black Sea Grain Initiative". Just Security. Retrieved 1 November 2023.
- ^ "Rule 53. Starvation as a Method of Warfare". ihl-databases.icrc.org. Retrieved 1 November 2023.
- ^ Dannenbaum, Tom (2021–2022). "Siege Starvation: A War Crime of Societal Torture". Chicago Journal of International Law. 22: 368.
- ^ "Unlawful Blockades as Crimes Against Humanity | ASIL". www.asil.org.
- ISBN 978-1-84832-090-1.
- ^ Richard Harding (2002). Seapower and Naval Warfare, 1650–1830. Routledge. Retrieved 7 February 2013.
- ^ Anderson p.381-83
- ^ Corbett p.86
- ^ was actually the result of international politics: the English blockade of New France forced the French to slip though this passage.
- ^
Nester, William R. (7 May 2014). "The French Empire". The French and Indian War and the Conquest of New France. Norman: University of Oklahoma Press. p. 89. ISBN 9780806145730. Retrieved 22 March 2025.
During the French and Indian War, with Canada's population swollen by several thousand more unproductive mouths to feed, starvation stalked the colony if the supply fleet did not arrive by late spring. For the war's last three years, stomach-pinched Canadians spent months vainly scanning the Saint Lawrence before a few ships finally appeared that managed to evade the British blockade.
- ^ Vego, Dr. Milan (2009). "Naval Classical Thinkers and Operational Art". Naval War College. pp. 4, 8. Archived from the original on 31 January 2017. Retrieved 22 March 2025.
Based on his study of naval history, Mahan contemplated two main methods in obtaining and maintaining command of the sea: decisive battle and blockade. [...] Corbett believed that the principal methods for securing control of the sea are by obtaining a decision and by conducting a naval blockade.
- ^ Palmer, Michael A., Command at Sea: Naval Command and Control since the Sixteenth Century, Harvard University Press, Cambridge, 2005, p.22
- ISBN 1-55750-715-5.
- ISBN 1-58477-609-9.
- ^ Encyclopædia Britannica, 11th edition. 1911. "Pacific Blockade", vol. 20, p. 433-434.
- ISBN 90-411-0036-9.
- ^ "San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994". ICRC.org. Archived from the original on 19 July 2006.
- ISBN 1-86189-202-0.
- Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica (11th ed.). Cambridge University Press.