In his Colonial Blockade and Neutral Rights, 1739–1763 (1938), Richard Pares noted that the classic age in the struggle between land power and sea power occurred in the middle years of the eighteenth century and that one of the results of this was that the same period became the classic age in the development of international maritime law. During the two great colonial wars, the War of the Austrian Succession and the Seven Years' War, important doctrines on contraband, blockade, and colonial trade, advanced by theorists like the Dane Martin Hupner, were defined by English and Continental jurists in a long series of opinions in prize cases and the like. These definitions were in turn embodied in government pronouncements and treaties to build up reference points for the future. As Pares noted at the close of his work, "for Admirals, for Foreign Ministers, and for judges, [these wars] were the dress rehearsals for greater struggles to come." By implication at least, this view was taken up much later by Max Savelle in his The Origins of American Diplomacy (1967), in which he examined the international history of the European and particularly the British colonies in America from 1492 to the end of the Seven Years' War in 1763.
At the beginning of this war, as both Pares and Savelle noted, the neutral powers assumed that free ships made free goods and that they would be able to continue their lucrative trade with the belligerents as if nothing had happened. This was not, however, the British view. In response to the neutral position, the British developed what came to be known as the Rule of the War of 1756, which drew a distinction between trading with the enemy and trading for the enemy. The former was to be regarded as permissible so that trade that would have been carried on in peacetime remained free and uninterrupted during war. The latter, however, was not permissible and the British reserved the right to interfere with any trade in war matériel that would not have been carried on in peacetime. During 1757 and 1758, however, it became obvious to the British that even this rather strict rule was being continuously evaded by transferring contraband from one ship to another. The response to this problem was to promulgate a supplementary order that became known as the doctrine of continuous voyage. This rule laid down the principle that for a confiscatable cargo to begin a voyage in one ship and then to continue "in the ship of a friend" made no difference, for the British government would regard such a voyage as a continuous one. In other words, it was the cargo and not the ship that mattered.
These principles governed the actions of the British government and their navy throughout the Seven Years' War. From their point of view, it was a simple problem: in Pares's words, "English trade had nothing to gain from the vindication of neutral rights." In addition, the British war effort might be placed in considerable jeopardy by adherence to the principles being espoused by the French foreign minister, Etienne François, duc de Choiseul, in his attempts to win over the neutral powers. These powers did not take the same view of the problem as the British. Although Choiseul and his agents discovered that the neutral position was by no means a united one, there was yet sufficient feeling of grievance against Great Britain among all the neutral powers in Europe to make the construction of a maritime league of neutrals a serious proposition. The British desired to establish overwhelming power at sea and were not altogether unsuccessful in their attempts to do so.
It was to the creation of such a league that the French government, posing as the champion of the neutrals, bent its energies in the early years of the war. It was a difficult and ultimately fruitless task, but in many ways it provided the model for the League of the Armed Neutrality of 1780.
There were precedents for a league of neutrals, especially in northern Europe where, as early as 1690, Denmark and Sweden had combined to try to enforce their concept of neutral rights in the Baltic, the area where a league of neutrals stood the greatest chance of success. It could easily be closed to the shipping of nations refusing to respect neutral rights, much to the disadvantage of, in particular, the British, who at this time were beginning to rely increasingly on Baltic naval stores. The Danes, however, also relied heavily on the income they gained from dues collected on the Sound, and the Baltic trading nations as a group were growing more dependent on their naval stores industries. Nevertheless, the French concentrated on this area, especially in view of the agreement on neutral rights signed by Denmark and Sweden shortly before hostilities began.
William Pitt the Elder, the British prime minister, was forced to make some concessions to neutral protests lest these powers respond favorably to French efforts to form a maritime league. But the French were to fail through the weakness of the neutral position, the unwillingness of the British to recognize claims not already granted by treaty, and the resultant reluctance of the neutrals to make a firm commitment to a maritime league. Not only was the Baltic project doomed almost from the beginning—the Danes, for example, would never actually say that free ships made free goods—but attempts to put together a wider league met with equal reluctance to participate. Whatever their long-term interests might have appeared to dictate, whatever blandishments the French used on them, the neutrals, and particularly the Danes and the Dutch, always lacked sufficient confidence in their own ability or that of the French to uphold the principles with which they were flirting. They were always too reliant on British friendship, or at least noninterference, in maintaining their overseas trade to give unequivocal assent and support to a league that might oblige them to sacrifice concrete gain for abstract principles. By the spring of 1759, Choiseul had essentially given up the attempt, despite a rather half-hearted effort a few months later.
In many ways, as Pares noted, the events of the Seven Years' War were a rehearsal for later wars. In the War of American Independence and later struggles, both neutrals and belligerents appealed to the body of maritime law developed in the years up to 1763. As in the past, efforts to set up a maritime league of neutrals, a concept that became a reality in only a limited sense, foundered, like later attempts, on the rock of national self-interest. In one important respect, however, the league of 1780 differed from attempts made by Choiseul and the French to bring together a group of neutral powers in the 1750s. It may be this difference that goes a long way toward explaining its success, if not in limiting the belligerents' interference with neutral shipping then at least in providing mediation aimed at bringing the American war to a close.