Neutrality. Neutrals are states which in time of war take no part in the contest, but continue pacific intercourse with both belligerents. The aim of the doctrine of neutrality is to reconcile the right of belligerents to carry on their warlike operations with the no less undeniable right of other nations to pursue peacefully their ordinary business. For many years after the rise of modern international law the conduct of warfare was discussed only with reference to belligerents, and no intermediate relation between an ally and an enemy was recognised. Not, indeed, till the middle of the 18th century did the terms 'neutral' and 'neutrality' come into general use; for not till then was a systematic effort made to regulate the relations of belligerents to nations standing aloof from the war, or to define their reciprocal rights and duties.
As between belligerent states and neutral states, the principles whence spring the complicated rules of modern neutrality are in themselves extremely simple. On the one hand, the neutral, being neither judge nor party, must show absolute impartiality in his dealings with both belligerents; on the other hand, the belligerent must pay scrupulous respect to the sovereignty of his neutral neighbours. Accordingly, throughout a war, neutrals continue diplomatic intercourse with both belligerents. A neutral state is not permitted to give armed assistance to either belligerent, even though such aid may have been promised before the war; nor to lend money to either side or guarantee such loan; nor to allow the passage of belligerent troops through its territory. A neutral is bound to prevent and cancel all acts of hostility, either in the neutral territory itself or in the adjacent waters, and to prohibit the exercise of any belligerent jurisdiction therein. So, if an attempt be made by troops of either belligerent country to traverse neutral territory, the neutral state is bound to disarm and intern such troops, and to set at liberty all prisoners of war found within its borders. Should a neutral state deviate from its duty in any of these particulars, the state injured is entitled to treat such deviation as a just cause of war. On the other hand, a belligerent is not permitted to carry on hostilities within neutral territory; nor to use neutral harbours for the purpose of fitting out expeditions against his enemy. He must scrupulously observe all the regulations of neutral states regarding the admission of cruisers or prizes into their ports.
The relations of belligerent states to the private citizens of neutral states involve greater difficulties. On land the property of neutral individuals is, of course, protected from belligerent attack; to this rule an exception is furnished by the Right of Angary (Low Lat. angaria, 'forced service'), under which a belligerent may seize the property of a neutral found in the territory of the other belligerent, and make use of it for the purpose of warlike operations, subject to his paying compensation. At sea, however, the commercial interests of belligerent and neutral merchants are so interwoven that it is difficult to separate them and strike at an enemy without injuring a friend; hence ever and again have arisen bitter controversies regarding the extent of a belligerent's power over the property of neutral citizens at sea. Two distinct principles for regulating the maritime capture of neutral property have at different times prevailed. By the one principle, the nationality of the ship determined liability to capture, so that neutral goods on hostile ships were liable to confiscation, while hostile goods on neutral ships went free. By the other principle, the nationality of the property determined its liability, so that neutral goods went free even though found on hostile ships, and hostile goods were liable to seizure even though found on neutral ships. In 1856 the Declaration of Paris finally settled the question by providing (1) that the neutral flag should cover an enemy's goods, except contraband of war; (2) that neutral goods, except contraband of war, should not be liable to capture even under the enemy's flag. The law, as thus settled, is the old rule, 'Free ship, free goods,' without the corollary, 'Hostile ship, hostile goods.' Attempts had frequently been made at an earlier period, particularly by Prussia in the Silesian Loan controversy and by the Armed Neutralities of 1780 and 1800, to incorporate the rule into international law; it was, indeed, mainly through the opposition of Great Britain that its final acceptance was postponed till 1856.
To the general rule of maritime capture, as thus determined, several important exceptions must be noted. Belligerents continue to have the right of intercepting, even on board of neutral vessels, such articles as are deemed contraband of war. The test to be taken in deciding what goods are contraband has been much discussed and is now quite unsettled (see CONTRABAND). The vessel, too, carrying the goods may be condemned along with its contraband cargo, where both belong to the same owner, or where false papers are found, or any other fraudulent device is resorted to. Another instance in which a belligerent is entitled to interfere with the ships and property of neutral individuals is furnished by the law of blockade (see BLOCKADE). Again, if during a war ships belonging to neutral citizens perform certain classes of services on behalf of one of the belligerents, the other belligerent is entitled to confiscate these ships. Among such hostile services, against which a belligerent is entitled to protect himself, are reckoned the transmission of naval signals or messages, the carriage of military and naval despatches, and the transportation of belligerent officers or troops. Where a citizen of a neutral state engages in any forbidden ventures—whether it be carrying contraband goods, running a blockade, or doing other un-neutral service—the aggrieved belligerent does not complain to the neutral state, but strikes at the neutral citizen directly by capturing his property and condemning it in his own prize court. The neutral state does not appear in the matter at all, unless the penalty imposed by the prize court be such as is not warranted by international law; in this case the neutral state claims reparation for its injured subject from the offending belligerent.
The most unsettled part of the modern law of neutrality is that dealing with the obligations, imposed on a neutral state, of restraining the conduct of its own citizens and of enforcing the due observance of neutrality on all persons within its jurisdiction. In recent times the tendency has been towards a large extension of the duties of neutral states in this respect. The movement was commenced by the Neutrality Act of the United States, passed in 1794, and re-enacted, with additions, in 1818. The principles of these American statutes have been closely followed in the series of British Foreign Enlistment Acts, passed with a view of arming the British government with sufficient power to enable it to fulfil the extended obligations of neutrality. Among the more important offences against neutrality which are now struck at by the municipal law of most states are such acts as the following: To leave the neutral territory in considerable numbers for the purpose of enlisting in the service of a belligerent; to accept letters of marque from a belligerent; to fit out within its territory armed expeditions against a belligerent, or increase therein the warlike force of any belligerent ship or expedition. At the same time a neutral state is not bound to restrain its subjects from trade in arms and munitions of war. The extent of the responsibility of neutral states for the building and fitting out of ships within their territory appears still to be uncertain. Till lately the English idea seems to have been that the neutral government was under no obligation to stop such proceedings, unless the vessel was ready to commence hostilities at the moment of its leaving neutral waters. But the events connected with the escape of the Alabama (see ALABAMA) and her sister-cruisers during the American civil war showed the inadequacy of this view. The treaty of Washington, 1871, by which all these questions were referred to arbitration, directed the arbitrators to apply, in addition to the ordinary rules of the law of nations, three new rules, known as the Rules of Washington. These rules, owing to their loose phraseology, have raised more questions than they have solved, but their general effect is immensely to extend the duties of neutral states.
See Hall, International Law (2d ed. 1884) and The Rights and Duties of Neutrals (1874); Wheaton, International Law (Eng. ed. by A. C. Boyd; 3d ed. 1889). For the history of the growth of the law of neutrality, see Manning, Law of Nations. See also the Letters of Historicus, and the works cited at ENEMY.