Formed in the spring and summer of 1780, the League of the Armed Neutrality was the first genuine league of neutrals formed because of complaints of the neutral powers against the major belligerents—with the possible exception of the United States. Although, in this respect as in others, the United States was of rather limited importance to anyone except Great Britain, France, and Spain, there is some evidence that the activities of American privateers were partly responsible for the movement to form a league of neutrals.
From the beginning of the war, Great Britain, still supremely, though as it turned out misguidedly, confident in the ability of its navy to hold the world at bay, had reverted to the maritime doctrines it had espoused in the past; and its actions had provided a constant source of complaint for the Danes and the Swedes as well as the Dutch and, later, the Russians. After the entry of France and Spain into the war in 1778, France made attempts to conciliate the neutrals as it had done in the Seven Years' War. Spanish policy hovered somewhere between the two. Whatever the avowed policies of the belligerent powers, however, they all, in varying degrees, offended the neutrals and produced a growing sense among them that some kind of joint expression of disapproval and firm resolve to take action was necessary to protect their interests.
Ultimately, leadership in this project was provided by Catherine II of Russia, who, under pressure from Great Britain on the one hand to enter an alliance and from the northern powers on the other to help protect their neutrality, found her own shipping becoming more subject to interference from the belligerents. The result was the declaration of 1780, identifying the principles by which Catherine proposed to act and the means—commissioning a substantial portion of her fleet to go "wherever honour, interest, and necessity compelled"—by which she proposed to enforce those principles. Broadly, these principles were that neutral shipping might navigate freely from port to port and on the coasts of nations at war; that the property of subjects of belligerent states on neutral ships should be free except when it was classed as contraband within the meaning of the Anglo-Russian Treaty of 1766; and that a port was assumed to be blockaded only when the attacking power had rendered its ships stationary and made entry a clear danger.
Through the summer of 1780, other neutral powers issued similar declarations, and the belligerents protested that they had always treated and always intended to treat Russian shipping according to these principles. By August, Denmark and Sweden, by almost identical agreements, had joined Russia in conventions establishing an armed neutrality, and, beginning with the Dutch United Provinces in January of the following year, most of the major neutrals of Europe acceded to the league before the end of the war. Of these powers, only the Dutch were obliged, at least partly because of their joining the league, to go to war with Great Britain. In this case, Catherine and her allies agreed to regard the Dutch as neutrals in their dealings with France and Spain to mitigate the effects on them of war with the British. Even so, the Dutch suffered severely from the war which, despite repeated attempts at mediation by Catherine and other members of the league, dragged on into the early summer of 1784 before Great Britain and the United Provinces finally signed a treaty of peace.
What, in the end, did the league achieve? Its existence made little, if any, difference in the attitude of the British navy in dealing with neutral shipping. Indeed, in the case of the United Provinces, adherence to the league was at least partly responsible for a far more serious situation than that nation might otherwise have faced. Any slackening in British depredations on the neutrals in general was perhaps due more to the declining effectiveness of the British navy, to the ineptitude of those running the war effort, and to the appearance of France and Spain on the rebel side than to the unity and effectiveness of the league. Nevertheless, resentment against the Rule of the War of 1756 was still strong among the Continental powers, and when, after 1778, the British escalated their actions against neutral commerce, they reacted in a way that, strengthened by Catherine's firm support, resulted increasingly in British isolation. As Paul Kennedy notes, in 1783 even Portugal and the Two Sicilies joined Russia, Prussia, Austria, Sweden, and Denmark in the league, leaving Britain completely isolated, a situation that led the scholar G. S. Graham to comment that it was the principal factor in the British defeat. It is at least clear that the mediation of Catherine and Joseph II of Austria was partly responsible for the treaties that ended the war in the fall of 1783.
This was probably the limit of the achievements of the first armed neutrality. It had little or no influence on American affairs and diplomacy in general, beyond the threat it imposed on the British. For the United States, as for other nations, it provided a set of principles of maritime law that were useful when they became convenient or necessary but that were to be discarded when neither of these conditions existed. At the end of the war, Charles James Fox, the British foreign secretary, proposed drawing up a treaty embodying the principles of armed neutrality, but his plan came to nothing. Ten years later, with Europe once again at war, Sweden and Denmark signed a convention renewing the provisions of the Armed Neutrality; but Catherine had already concluded an alliance with Great Britain, which, by virtue of the fact that one of its objects was to destroy French commerce, deliberately ignored the principles of the league.