BLOCKADE has been defined 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." It differs from a "pacific blockade" (q.v.) 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 one undertaken to attain some specific military objective, e.g., the capture of a naval port. A "com mercial blockade" has no immediate military objective but is de signed to cause the enemy to surrender or come to terms by cutting off all commercial intercourse by sea. A belligerent may, if he can, blockade the whole of the enemy's seaboard, hut 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 he blockade enemy territory in such a way as to prevent access to neutral territory.
The common law of blockade rests mainly upon the principles laid down by the Anglo-American Prize Courts, the more impor tant of which are summarized in the judgments of Dr. Lushington and of the Privy Council in The Fransiska, Spinks III; io Moo. P.C. 3 7. 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.
(I) A blockade must be duly established, i.e., it must be in stituted under the authority of the belligerent Government. Us ually the officer in command of the naval force institutes the blockade under express instructions, but if he does so without them—an unlikely occurrence in modern times—his action must be ratified by his 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 block ade is officially proclaimed. The officer in command must also notify the local authorities and the foreign consuls. (2) It must be effective. Paper blockades were declared illegal by the Decla rations of the Armed Neutralities of 1780 and 180o, and it was to suppress their subsequent continuance that Art. 4 of the Declaration of Paris 1856 (q.v.) provided that "blockades in order to be binding must be effective," i.e., maintained by a force sufficient really to prevent access to the coasts of the enemy. The Continental view demanded a stricter standard of sufficiency than the Anglo-American. The latter, however, ultimately prevailed.
(3) It must be continuously maintained and impartially enforced against all vessels alike. If interrupted—except when temporarily interrupted by adverse weather—it must be duly re-established. Certain classes of vessels are exempt from the latter part of this rule, viz., neutral warships and neutral vessels carrying distressed seamen of their own nationality sent home by the resident minister of the neutral State, and neutral vessels compelled by stress of weather, need of provisions or repairs to put into the blockaded port. Under the Anglo-American practice vessels which have re ceived a special licence from the Government of the blockading State or the commander of the blockading force are also exempt.
(4) There must be some violation either by egress or ingress by the vessel. At the London Naval Conference of 1909 it was gen erally 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 notified notice will be presumed, if there has been sufficient time for the vessel to receive it, since it is the duty of the neutral Govern ment to communicate such notice to its subjects. If the block ade is de facto, express notice must be given to the vessel by the blockading force and endorsed on the ship's papers. (5) There must be actual or constructive knowledge of the blockade by those responsible for the conduct of the vessel.
A blockade terminates (I) if it is expressly raised by the blockading Government or by the officer in command of the blockading force; (2) if it ceases to be effectively maintained; (3) if the blockaded place is actually occupied by the blockading State.
The penalty for breach of blockade was the loss of the ship in any event, and of the cargo if at the time of shipment the block ade was known or might have been known by the shipper : The Panaghia Rhomba, 12 Moo. P.C. 168; Scott, 951 (1858).
At the London Naval Conference, 1908, an attempt was made to codify the law of maritime warfare. The provisions in the Declaration of London, 1909, relating to blockade are substantially merely declaratory of the common law. Two important amend ments, however, were made. By Art. 17 neutral vessels may only be captured for breach of blockade "within the area of the war ships assigned to render the blockade effective." Under the cus tomary law they are liable to capture during any part of the out ward or return voyage. By Art. 19 the doctrine of continuous voyage was declared inapplicable to blockade. Although the Declaration had not been ratified by any State, it was, subject to some additions and modifications, adopted by all the belligerents at the commencement of the World War. On Feb. 4, 1915, Ger many declared its submarine blockade against Great Britain, and on March 1, the British Government announced that it was the intention of the Allied Governments as a retaliatory measure "to seize all ships carrying goods of presumed enemy destination, ownership or origin." Although in effect blockades, neither of these measures was legally a blockade, since they did not conform to the provisions of the law of blockade. By the withdrawal of the Declaration and subsequent Orders by the Maritime Rights Order in Council, July 17, 1916, and by reliance upon the law of contraband, the situation was regularized for the Allied Govern ments.
For the controversy between Great Britain and the United States upon the so-called blockade of Germany, see Parl. Pap. (Cd. 7816), and (Cd. , In the last hundred years the methods of enforcing blockade have changed as much as ships themselves, but command of the sea is still the essential condition.
In the wars of the 17th and 18th centuries, blockade was en f orced by maintaining squadrons in the vicinity of the enemy ports, the most notable example being the British blockade of the French and Spanish ports from the outbreak of war in 1803 to its close in 1814. This blockade foiled Napoleon's plans for the invasion of England, because it prevented Villeneuve from making a junction with the divisions in Brest and Rochefort, after he had slipped out of Toulon and drawn Nelson to the West Indies and back after him. On Villeneuve's return in August 1805 Napoleon at once recognized that his invasion plans had miscarried and on Sept. 1, the Grand Army, which he had con centrated on the heights above Boulogne, was marched off into Germany. It was not until Oct. 21 that the greater part of the combined French and Spanish fleet was destroyed at Trafalgar (q.v.), the remnant being locked up in harbour till the end of the war by the blockade.
Napoleon's fleet being disposed of, British sea-power entered on a desperate struggle with his land power expressed in terms of commercial blockade. This conflict eventually (1812) landed Britain in a war with the United States, and drew Napoleon into the expedition to Russia which caused his downfall. The points of similarity and contrast between that long economic struggle and the one in the World War afford an interesting study.
In the Russo-Japanese War 0904-05) the Japanese fleet did maintain a close blockade of Port Arthur, but suffered severely from submarine mines. There were then no submarines or aircraft.
A nation fighting for its existence and depending for success on its maritime superiority cannot afford to see one of the main objects for which its naval strength was developed largely dis counted by neutrals who, ostensibly taking no part in the struggle, supply its enemy with the sinews of war.
The ultimate aim of a sea Power is to protect its own sea communications while denying oversea supplies to the enemy. The right of a belligerent to stop contraband of war from going to its enemy has always been admitted, but it is not unnatural that the weaker maritime Powers and neutrals should prefer that goods carried in neutral ships should be secure from capture, that is the principle that "the flag covers the goods" or "free ships, free goods." During the hundred years that followed Napoleon's downfall Great Britain was almost invariably a neutral and her own commercial interests found profit in this latter view. Her statesmen, who might have had longer vision, sacrificed this vital belligerent right by signing the Declaration of Paris in 1856. "I believe" said the late Lord Salisbury speaking in the House of Lords on March 6, 1871, "that since the Declaration of Paris, the fleet, valuable as it is for preventing an invasion of these shores, is almost valueless for any other purpose." A further check on the use of Britain's sea-power for preventing supplies from going to the enemy was the Declaration of London. Of the two descriptions of articles enumerated in this instrument, the absolute contraband list was small, being confined to articles of exclusive military value such as guns, explosives, etc. These were liable to capture when destined to the enemy in neutral ships either direct or through neutral territory and in this case the doctrine of continuous voyage was recognized.
The conditional contraband list was composed of articles neces sary to the civil population as well as to the military forces, such as food, fuel and clothing. This was liable to capture only if shown to be destined for the armed forces or to a government department of the enemy State, and provided it went direct to an enemy port. It could not be touched if discharged in a neutral port for transmission by rail or inland waterway. The evidence required by the declaration to prove the innocence of a cargo could so simply be evaded as to render this class of goods prac tically immune from capture, and in this case even the doctrine of continuous voyage was disallowed.
International law as it existed in 1914 only recognized blockade based on the conditions of a hundred years ago, so the closing of the outer seas to the shipping of the Central Powers and to absolute contraband as defined in the Declaration of London was of itself insufficient to affect them really seriously. Though the British Admiralty had given consideration to this matter of blockade the mechanism of modern seaborne commerce is too intricate to be controlled by naval means alone, and little provision had been made for building up an adequate organization. The Declaration of London had never been ratified by any Power, but it was adopted by Great Britain in agreement with France and Russia by Order in Council of Aug. 20, 1914. The absolute contraband list had indeed been enlarged and the doctrine of con tinuous voyage extended to conditional contraband. The method of consignment had also been rendered more strict, but even so Lord Salisbury's fears of 1871 proved to be only too well justified!