This article investigates the formal purpose of declaring wars for Hugo Grotius. Grotius was adamant that states always use justification in a duplicitous way to conceal their real motivation to go to war. As such, the purpose of declaration is not to assert the just cause of war. Rather, what any public declaration does, is provide recognition that confers legal validation to the disputing parties. The legal rules of war were described by the law of nations and occasionally permitted states to commit certain ‘war crimes’ with impunity. For Grotius, this was not a moral sanctioning of such crimes but rather a means to prevent the occurrence of wars, which such endless repudiations risked causing or exacerbating. Grotius’s concern for the effects of war is conspicuous; and recounting his maxim that war should always be a last resort, this article argues that declaration of war has a distinct moral purpose for Grotius. In fact, public declaration of war is, together with constraints on the conduct of war, a ‘principle of moderation’ Grotius insists should be upheld in times of war. Declaration of war gives the parties avenues to seek peace and reconciliation, and, therefore has a humanitarian purpose for Grotius by ultimately seeking to prevent the disparaging effects of war. Even in wars that do not demand a public declaration, such as those regulated by natural law such as punitive wars or defensive wars, Grotius cautions that declarations of war are advisable. The remaining lingering issue is how to engage with unlawful enemy combatants, such as pirates - a distinct problem that the international community still faces with increasing regularity. Grotius was certainly aware of the legal (and moral) consequences of recognising belligerency we cannot possible hope to build moral relations with, and, this article claims, ‘unlawful’ enemies ultimately demarcates the boundary of international society.

本文研究了对雨果·格罗蒂乌斯宣战的正式目的。格罗蒂乌斯坚持认为，国家总是以一种愚蠢的方式使用称义来掩盖其发动战争的真正动机。因此，宣布的目的不是断言战争的正当理由。相反，任何公开声明所做的就是提供承认，使争端各方获得法律确认。战争的法律规则由国家法律描述，偶尔允许各州不受惩罚地犯下某些“战争罪行”。对于格罗蒂乌斯来说，这不是对此类罪行的道义制裁，而是防止战争发生的手段，而这种无休止的否定行为有可能引起或加剧战争。格罗蒂乌斯对战争影响的关注是显而易见的。并重申他的格言：战争永远是万不得已的选择，本文认为，宣战对格罗蒂乌斯有独特的道德目的。实际上，公开宣战，加上对战争进行的限制，格罗蒂乌斯坚持在战争时期应坚持“节制原则”。《宣战》为双方提供了寻求和平与和解的途径，因此，格罗蒂乌斯通过最终寻求防止战争的毁灭性后果而对格罗蒂乌斯具有人道主义目的。即使在不需要公开宣布的战争中（例如惩罚性战争或防御性战争等受自然法规范的战争），格罗蒂乌斯也警告说，宣战是可取的。剩下的挥之不去的问题是如何与海盗等非法敌方战斗人员交战，这是国际社会仍在日益增加的规律性下面临的一个独特问题。