The Rights of War and Peace

by Hugo Grotius

IX. A declaration of war, made against a sovereign, includes not only his own subjects, but all who are likely to become his associates, as thereby they make themselves accessories in the war. And this is what the modern lawyers mean, when they say that, in bidding defiance to a Prince, we bid defiance to all his associates. For they give the name of defiance to a declaration of war. By which is understood the war carried on with the power against whom it has been declared. Thus upon war being declared against Antiochus, there was no occasion for a separate declaration against the Aetolians, who had openly joined Antiochus. For, as the heralds in their answer justly observed, the Aetolians had, by that act, voluntarily brought war upon themselves.

X. But if after the conclusion of such a war it should be deemed expedient to attack any other nation or king for having furnished supplies and assistance towards that war, a new declaration of war will be necessary. For that nation or king is then to be considered, not as an accessory, but as a principal enemy. And therefore it was with reason said, that the war of Manlius against the Galatians, and that of Caesar against Ariovistus, were not just wars according to the law of nations. For war was made upon them not as accessories, but as principals. So that for this purpose, as the law of nations would have required a declaration, in the same manner the Roman law would have required a new order of the Senate.

For on the motion being made for the war with Antiochus, the question was also put, whether it should not at the same time be made with his adherents. The same rule also being observed against King Perseus, it must be understood, as including the adherents during all the time that war with those princes continued; and implicating all, who in reality gave them support.

XI. The reason why a declaration is necessary to constitute what is deemed, according to the law of nations, a just war, is not that which some writers assign. For they allege that it is to prevent every appearance of clandestine and treacherous dealing: an openness, which may be dignified with the name of magnanimity, rather than entitled a matter of right. On this point, we are informed that some nations have gone so far, as to settle and make known the very time and place of a general engagement.

But waving all conjecture, a more satisfactory reason may be found in the necessity that it should be known for CERTAIN, that a war is not the PRIVATE undertaking of bold ADVENTURERS, but made and sanctioned by the PUBLIC and SOVEREIGN authority on both sides; so that it is attended with the effects of binding all the subjects of the respective states;—and it is accompanied also with other consequences and rights, which do not belong to wars against pirates, and to civil wars.

XII. There is much truth indeed in the observations, which some have made, and which they have produced examples to confirm, that even in wars of this kind all captures become the lawful prize of the captors.

Yet this is only partially true, and that too, according to the law of nature, and not according to the voluntary law of nations. For the latter only makes provision to secure the rights of nations, as WHOLE communities, and not of those, who, as in civil wars, form but ONE PART of a nation.

The same writers are mistaken too in the supposition that defensive wars require no declaration. For it is no less necessary to shew by way of vindication that it is a defensive war, and at the same time by public declaration to give it the character of a national and lawful war, in order to establish those rights and consequences, that have been already mentioned, and which will hereafter be more fully explained.

XIII. They maintain another position also, which is by no means true, and that is, that a power ought not IMMEDIATELY to follow up a declaration of war with actual hostilities, as Cyrus did to the Armenians, and the Romans to the Carthaginians. For the law of nations requires the intervention of no DEFINITE time between the declaration and the commencement of war.

There may indeed be some cases, where natural justice will render such a delay proper. Thus, for instance, where reparation for injury, or the punishment of aggressors is demanded, it is but reasonable to wait till it can be known, whether the just demand will be complied with or rejected.