封鎖 | 定義、例、国際法

Blockade | Definition, Examples, & International Law | Britannica Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos blockade Introduction & Top Questions International law regarding blockades Examples of blockades in war Blockade in the American Civil War Blockade in World War I Retaliation Blockade through exercise of sovereign rights Bunker control Embargoes Blacklists and the financial blockade Rationing World War II Later blockades References & Edit History Quick Facts & Related Topics Images & Videos At a Glance blockade summary Related Questions What is a blockade? Are blockades legal? What are the types of blockades? What are the legal requirements for a blockade? 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External Websites Britannica Websites Articles from Britannica Encyclopedias for elementary and high school students. blockade - Student Encyclopedia (Ages 11 and up) CSS Alabama and USS Kearsarge in battle Battle between the Confederate blockade runner Alabama and the Union's Kearsarge in the harbour of Cherbourg, France; painting by Édouard Manet, 1864. (more) blockade warfare Ask Anything Quick Summary Homework Help Also known as: naval blockade Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Apr. 13, 2026 • History Britannica AI Ask Anything Quick Summary Table of Contents Table of Contents Quick Summary Ask Anything Top Questions What is a blockade? A blockade is an act of war where one party blocks entry to or departure from a defined part of an enemy’s territory, usually its coasts. Blockades are regulated by international law and custom and require advance warning to neutral states, impartial application, and effective and continuous maintenance (the blockading party must have adequate forces in place to intercept the bulk of incoming and outgoing traffic). It is insufficient for a belligerent to simply declare a country to be under blockade (a so-called “paper blockade”) if it lacks the power to enforce it on a consistent basis. Are blockades legal? Blockades are legal under international law, but they are unquestionably acts of war. The laws governing the application and enforcement of naval blockades are derived from rulings of Anglo-U.S. prize courts in the 19th century as well as a series of naval treaties that were concluded in the early 20th century. To satisfy these requirements, a blockade must be: openly declared to the government that is being subjected to the blockade; effective and continuous (the blockading party must have sufficient forces in place to intercept naval traffic); and it must be impartially applied to all vessels. What are the types of blockades? Blockades can be military or commercial. A military blockade aims for a specific military objective, such as the capture of a port. A commercial blockade has no immediate military objective but is designed to cause the enemy to surrender or come to terms by cutting off all commercial intercourse by sea. Commercial blockades are more restrictive than embargoes or other acts of economic coercion. What are the legal requirements for a blockade? A blockade must be duly established, effective, continuously maintained, and impartially enforced. It must not block neutral territory unless controlled by the enemy. For a blockade to be considered effective, the blockading party must have sufficient forces in place to intercept the bulk of inbound and outbound traffic. This requirement stems from the use of so-called “paper blockades,” whereby a country would declare an entire coastline to be under blockade, even though it lacked the naval power to enforce such a threat consistently. How did blockades evolve during World War I? World War I saw blockades evolve with technological advances, including submarines and aircraft, making close blockades difficult and leading to long-range blockades. What was significant about the Berlin blockade? The Berlin blockade from June 1948 to May 1949 was significant as it was a land blockade by the Soviet Union, overcome by a massive airlift operation by the U.K. and U.S. News • Trump says US military has blockaded Iranian ports to pressure Tehran • Apr. 13, 2026, 7:37 PM ET (AP) ... (Show more) US military says it will blockade Iranian ports after ceasefire talks ended without agreement • Apr. 12, 2026, 9:52 PM ET (AP) Show less blockade , an act of war whereby one party blocks entry to or departure from a defined part of an enemy’s territory, most often its coasts. Blockades are regulated by international law and custom and require advance warning to neutral states and impartial application. International law regarding blockades English engraving celebrating the blockade of Louisbourg An English engraving from 1775 celebrating the blockade of Louisbourg, Nova Scotia, during the French and Indian War. (more) In a memorandum prepared for the London Naval Conference of 1908–09, the British government defined a blockade as “an act of war carried out by the warships of a belligerent , detailed to prevent access to or departure from a defined part of the enemy’s coast.” This differs from a so-called pacific blockade inasmuch as the latter is not strictly an operation of war and cannot rightly be enforced against neutrals. The former may be either military or commercial. A military blockade is undertaken to attain some specific military objective, such as the capture of a naval port. A commercial blockade has no immediate military objective but is designed to cause the enemy to surrender or come to terms by cutting off all commercial intercourse by sea. A belligerent may, if it can, blockade the whole of the enemy’s seaboard, but the mere proclamation of a blockade of the whole or any part of the enemy’s coast, without anything more, is of no legal effect. Such proclamations were formerly common and were known as “ paper blockades.” A belligerent may not blockade neutral territory unless it is in the actual control or occupation of the enemy, nor may it blockade enemy territory in such a way as to prevent access to neutral territory. The common law of blockade rests mainly upon principles laid down by Anglo-U.S. prize courts . The more important of these are summarized in the judgments of British jurist Stephen Lushington and Privy Council in an 1854 decision regarding the Franciska , a Danish ship that was seized by the British during the Crimean War . More From Britannica Napoleon I: Blockade and the peninsular campaign In order, therefore, to render a blockade valid under the common law and to impose penalties upon neutral vessels for breach of it, the following facts must be proved: A blockade must be duly established: that is, it must be instituted under the authority of the belligerent government. Usually the officer in command of a naval force institutes the blockade under express instructions, but if this is done without them—an unlikely occurrence—this action must be ratified by the government. In either case, although in the British view an official notification is not necessary, neutral powers are notified in practice through diplomatic channels and the blockade is officially proclaimed. The officer in command must also notify the local authorities and foreign consuls. The blockade must be effective. Paper blockades were declared illegal by the Declarations of the Armed Neutralities of 1780 and 1800, and it was to suppress their subsequent continuance that Article 4 of the Declaration of Paris (1856; a supplement to the Treaty of Paris ) provided that “blockades, in order to be binding, must be effective.” A blockade, therefore, must be maintained by a force sufficient to truly prevent access to the coasts of the enemy. The blockade must be continuously maintained and impartially enforced against all vessels alike. If interrupted—except when temporarily interrupted by adverse weather—it must be duly reestablished. Certain classes of vessels are exempt from the latter part of this rule, such as neutral warships and neutral vessels carrying distressed seamen of their own nationality, as well as neutral vessels compelled by stress of weather or the need of provisions or repairs to put into the blockaded port. Under the Anglo-U.S. practice vessels which have received a special license from the government of the blockading state or the commander of the blockading force are also exempt. There must be some violation either by egress or ingress by the vessel. At the London Naval Conference of 1909 it was generally agreed that there must be some notice, either actual or presumptive. In respect of egress the fact of blockade is sufficient. In respect of ingress, if the blockade has been officially declared, notice will be presumed if there has been sufficient time for the vessel to receive it. If the