Enemy. According to the doctrine of the civil law, as formulated by Ulpian (Digest 49. 15, 24), those alone are enemies 'who have publicly declared war against us or we against them; all others are thieves and robbers.' In the earlier ages of the Roman republic such a declaration was most solemnly made to the foreign state by the feciales or priests, who acted as guardians of public faith, and was always attended by elaborate religious rites. So now, in order to constitute an enemy, there must be a public declaration of war made by a duly organised state or kingdom. Jurists are, however, divided in opinion in respect to the necessity of a previous declaration to the enemy in the case of an offensive war. Grotius and Vattel recommend such a previous declaration of war to the enemy, as being required by justice and humanity, and the latter specially commends the fecial law of the Romans, as giving a sanction and solemnity to acts of belligerency. Bynkershoek, on the other hand, maintains that such a declaration is not required by the law of nations, and that, though it may very properly be made, it cannot be demanded as a matter of right. Since the time of Bynkershoek the practice of a solemn declaration made to the enemy has fallen into disuse, and the nation now contents itself with making a public proclamation of war within its own territory and to its own people. Some such formal public act is necessary to announce to the people at home their new relations and duties growing out of a state of war, and to apprise neutral nations of the facts, in order that they may conform their conduct to the new state of things. Under the British constitution, the sovereign alone declares war, but this prerogative of the crown is practically ineffectual, since, without the consent of parliament, the money requisite to carry on the war cannot be raised. It is still an open question whether war can be legally waged by states only in their corporate capacity and with their corporate resources, or whether it embraces the individual members of the states at war, and the property which belongs to them as private persons. The tide of modern opinion, however, seems to have set in the direction of the former and more humane theory. The doctrine of the older jurists was that, on the formal declaration of hostilities, all the subjects of the one nation became enemies to all the subjects of the other. From this principle there has been deduced the important consequence, as a recognised rule of international law, that the property of alien enemies residing in either of the hostile states, may be confiscated, and even that such persons may be detained as prisoners of war. The Americans, during the war with England, asserted this right in regard to British property found in their territory. But the usage of civilised nations for a long period has much modified the stern rule of law. It is provided in Magna Charta that, upon the breaking out of war, foreign merchants found in England, and belonging to the country of the enemy, should be attached 'without harm of body or goods,' until it should be known how English merchants were treated by the enemy; 'and if our merchants,' said the charter, 'be safe and well treated there, theirs shall be likewise with us.' The statute of staples, 27 Edw. III. chap. 17, made a still more liberal and precise enactment in favour of such foreign merchants residing in England. Forty days were allowed them, after the proclamation of war, to remove from the kingdom themselves and their goods, and if by reason of accident that time were not enough, forty days more were to be conceded to them. Vattel, among others, denounces the practice of confiscating the goods of alien enemies, and maintains that a state, having permitted foreigners to enter its territory, and to continue there, has tacitly promised them full liberty and security for their return. In modern times it has become the usual practice of nations thus to respect the property of individuals on the outbreak of war. Stipulations to this effect are an established formula in all commercial treaties, and, even when there is no treaty, such a liberal provision is often announced in the declaration of war itself.
According to ancient usage, the utmost cruelty was lawful towards enemies. In modern times more humane principles prevail, and men recognise that, by taking up arms against one another in public war, they do not cease on this account to be moral beings, and responsible to one another and to God. Warfare is now carried on subject to certain general rules, which are intended, as much as may be, to abridge the calamities of war, and to protect the rights of individuals. An admirable summary of these rules may be found in the Instructions for United States Armies, issued in 1863. These instructions were prepared by the celebrated jurist Francis Lieber, and have served as a basis for most of the subsequent compilations. In 1874 an International Conference held in Brussels devoted much time to the elaboration of rules for military warfare. Still more recently, the Institute of International Law, at its meeting at Oxford in 1880, prepared and adopted a Manual of the Laws of War on Land, in which minute rules for the conduct of hostilities are succinctly set forth. Military necessity admits of all direct destruction of life or limb of armed enemies, and of other persons where destruction is unavoidable in the armed contests of the war; it allows of all destruction of property, and obstruction of the ways and channels of traffic, and of all withholding of sustenance or means of life from the enemy. Such military necessity does not, however, admit of cruelty—i.e. the infliction of suffering for the sake of suffering, nor of maiming or wounding except in fight, nor of the use of poison in any way, nor of the wanton devastation of a district. It admits of deception, but disclaims all acts of perfidy. In the case of the occupation of a country by the enemy, the persons of the inhabitants, especially of women, are respected, and the maxims of religion and morality are acknowledged. Private property, unless forfeited by crimes, can be seized only on the ground of military necessity, and if the proprietor has not fled receipts are usually given, which enable the spoliated owner to obtain indemnity. Trade between the subjects of two hostile powers is absolutely suspended during hostilities, unless permitted by express sanction, and the importation of articles particularly useful in war is contraband. All such material, whether supplied by subjects of the enemy or of another state, is seized and confiscated. For other information on the rules and usages which regulate the relations of belligerent states, reference is made to the articles CONTRABAND OF WAR, BLOCKADE, NEUTRALITY, PRIZE, PRISONERS OF WAR, GENEVA, &c. As to the right of individuals to fit out vessels for the annoyance of the enemy, see PRIVATEER, and PIRACY.
Grotius, De Jure Belli et Pacis, lib. iii. chap. 3-7; Kent's Commentaries, vol. i. chap. 3; Bluntschli, Das moderne Völkerrecht; Sir Travers Twiss, Law of Nations in Time of War (Oxf. Clar. Press, 2d ed. 1875).