§ 215. Although the outbreak of war between States as a rule brings non-hostile intercourse to an end, necessity of circumstances, convenience, humanity, and other factors call, or may call, some kinds of non-hostile relations of belligerents into existence. And it is a universally recognised principle of International Law that, where such relations arise, belligerents must carry them out in good faith. _Fides etiam hosti servanda_ is a rule which was adhered to in antiquity, when no International Law in the modern sense of the term existed. But it had then a religious and moral sanction only. Since in modern times war is not a condition of anarchy and lawlessness between belligerents, but a contention in many respects regulated, restricted, and modified by law, it is obvious that, where non-hostile relations between belligerents occur, they are protected by law. _Fides etiam hosti servanda_ is, therefore, a principle which nowadays enjoys as well a legal as a religious and moral sanction. [Sidenote: Different kinds of Non-hostile Relations.] § 216. As through the outbreak of war all diplomatic intercourse and other non-hostile relations come to an end, it is obvious that non-hostile relations between belligerents must originate either from special rules of International Law or from special agreements between the belligerents. No special rules of International Law which demanded non-hostile relations between belligerents existed in former times, but of late a few rules of this kind have arisen. Thus, for instance, release on parole[429] of prisoners of war creates an obligation on the part of the enemy not to re-admit the individuals concerned into the forces while the war lasts. And, to give another example, by article 4 of the Geneva Convention of 1906, and article 14 of the Hague Regulations--see also article 17 of Convention X. of the Second Peace Conference--it is the duty of either belligerent to return to the enemy, by his prisoner-of-war bureau, all objects of personal use, letters, jewellery, and the like found on the battlefield or left by those who died in hospital.[430] Non-hostile relations of this kind, however, need not be considered in this chapter, since they have already been discussed on several previous pages. [Footnote 429: See above, § 129.] [Footnote 430: See above, § 144.] Non-hostile relations originating from special agreements of belligerents, so-called _commercia belli_, may either be concluded in time of peace for the purpose of creating certain non-hostile relations between the parties in case war breaks out, or they may be concluded during the actual time of war. Such non-hostile relations are created through passports, safe-conducts, safeguards, flags of truce, cartels, capitulations, and armistices. Non-hostile relations can also be created by peace negotiations.[431] Each of these non-hostile relations must be discussed separately. [Footnote 431: See below, § 267.] [Sidenote: Licences to Trade.]