The league was remembered in the United States, somewhat erroneously, as a mark of Russian friendship and sympathy, and bolstered Anglophobia in the two countries. More generally, it affirmed a cardinal principle of maritime law that continues in effect in the early twenty-first century. Indirectly, it also led to a considerable expansion of Russian-American trade from the 1780s through the first half of the nineteenth century.
Coming at this stage in the War for Independence, the Russian declaration boosted American morale and inspired the Continental Congress to dispatch Francis Dana to St. Petersburg to secure more formal recognition and support.
Denmark and Sweden, accepting Russia's proposals for an alliance of neutrals, adopted the same policy towards shipping, and the three countries signed the agreement forming the League. They remained otherwise out of the war, but threatened joint retaliation for every ship of theirs searched by a belligerent. When the Treaty of Paris ended the war in 1783, Prussia, the Holy Roman Empire, the Netherlands, Portugal, the Kingdom of the Two Sicilies and the Ottoman Empire had all become members.
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.
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.
Already annoyed by American privateer interference with Anglo-Russian maritime trade in the 1770s, Catherine the Great was even more frustrated by British countermeasures that intercepted and confiscated neutral shipping suspected of aiding the rebellious American colonies. In March 1780 she issued a Declaration of Armed Neutrality that became the basic doctrine of maritime law regarding neutral rights at sea during war. It defined, simply and clearly, the rights of neutral vessels, contraband (goods directly supportive of a military program), and the conditions and restrictions of an embargo, and overall defended the rights of neutrals (the flag covers the cargo) against seizure and condemnation of nonmilitary goods.
Russia was not only displeased with Britain. American privateers and French and Spanish ships also harassed Russian shipping. The policy was directed at Britain because Britain was causing the most trouble. Since France and Spain were viewed as neutral countries and America was not recognized as a country at the time, Britain was the main target.
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.
Catherine refused to trade with the American revolutionaries, but she had no such scruples with the Bourbon powers of France and Spain. When France and Spain went to war with Britain, they became avid consumers of Russian naval stores. This new and thriving trade increased traffic in the Baltic. The British used their naval power to try to halt the flow of these vital resources to their enemies. British warships stopped and searched merchantmen flying the flags of neutral countries, seizing goods they deemed contraband. This British arrogation of maritime authority injured the pride as well as the pocketbooks of the neutral states.
Ironically, it was the British government that first tried to involve Catherine in the American war. Russia had recently concluded a war with the Turks in 1775, and the British turned to Catherine as a potential purveyor of mercenaries, hoping to hire a number of her battle-tested regiments. Catherine refused to sell her soldiers, telling George III that he ought to find a way of subduing his rebellious subjects with his own men.
Catherine the Great, Empress of Russia, significantly influenced the course of the American Revolution. She had no sympathy whatsoever for the revolution, and her interest in the war had nothing to do with the Americans. Catherine's concern lay with the European balance of power. Early in the century, Peter the Great had set about engaging Russia with the west, and Catherine was intent on continuing this mission. The war that started in America affected Russia's economic interests and gave Catherine an opportunity to decisively assert Russian influence.