The Law of War and Peace (1625)

by Hugo Grotius

Who May Lawfully Wage War

I.     The efficient causes of war are in part those who wage war on their own account as principals.
As in other matters, so also in acts originating in the will, there are ordinarily three kinds of efficient causes-principal agents, auxiliary agents, and instruments.

In war the principal efficient cause is generally the person whose interest is at stake-in private war, the individual; in public war, the public power, in most cases the sovereign power. Whether war can be made by one on behalf of others who do not make war on their own account, we shall see elsewhere. Meanwhile we shall hold to this principle, that by nature every one is the defender of his own rights; that is the reason why hands were given to us.

II.     The efficient causes of war are in part those who wage war on another’s account, as auxiliary agents.
1.   But to render service to another, so far as we can, is not only permissible, it is also honorable. Those who have written on the subject of duties rightly say that nothing is more useful to a man than another man. There are, however, various ties which bind men together and summon them to mutual aid. Thus those who are related by kinship unite to assist one another. Neighbors, too, and those who belong to the same state, call on one another for help; hence the cry ‘Hither, Romans’ and the word ‘to call the Romans’ (quiritari). Aristotle said that every man ought to take up arms on his own behalf, if he had suffered wrong, or on behalf of his kindred or benefactors, or of his associates, in case wrong should have been suffered by them. It was the teaching of Solon that those commonwealths will be the most fortunate in which each citizen views the wrongs of others as his own.

2.   But in default of all other ties, the common bond of human nature is sufficiently strong. Devoid of interest to man is nothing that pertains to man. In the words of Menander:

      If we our strength should all together join,
      Viewing each other’s welfare as our own,
      If we should each exact full punishment
      From evil-doers for the wrongs they do,
      The shameless violence of wicked men
      Against the innocent would not prevail;
      Guarded on every hand, and forced to pay
      The penalties which their misdeeds deserve,
      They soon would cease to be, or few become.

Similar is this saying of Democritus: ‘Those who are oppressed by wrong-doing must be defended to the limit of our strength, and not neglected; for that is a work of justice and goodness.’ The thought is thus developed by Lactantius:

God, who did not impart wisdom to the other animals, made them more safe from attack and from danger by natural means of defense. But because He made man naked and weak, to the end that He might the rather equip him with wisdom, in addition to other gifts He gave to man this feeling of mutual regard, that man should defend, should love, should protect man, and should both receive and furnish help against all dangers.

III.     The efficient causes of war are in part those who wage war as instruments, as servants and subjects.
When we use the word ‘instruments’ in this connection we do not mean ‘weapons’ and similar things; we mean persons whose acts of will are dependent on the will of another.

An instrument, as we use the term here, is a son in relation to his father, viewed as by nature a part, so to speak, of the father; such an instrument also is a slave in relation to his master, a part, as it were, in a legal sense. For just as a part is a part of the whole not only in the same relation that the whole sustains to the part, but also the very thing which constitutes a part pertains to the whole, so possession becomes something of the possessor. Says Democritus, ‘Use slaves just as parts of the body, one for one purpose, another for another.’ What a slave is in the household, a subject is in the state, an instrument, accordingly, of the ruler.

IV.     By the law of nature no one is enjoined from waging war.
There is no doubt that by nature all subjects may be used for purposes of war; but certain classes are exempted by special enactment, as formerly slaves; at Rome, now men in holy orders generally. Nevertheless a special enactment of this kind, as such laws generally, must be understood as subject to exception in cases of extreme necessity.

Let these general statements in regard to auxiliary agents and subjects suffice; for the special questions relating to them will be treated in the proper connection.