[Footnote 47: It should be mentioned that the United States did not sign the Declaration of Paris because it did not go far enough, and did not interdict capture of private enemy vessels.]
§ 48. The next period, the time from 1856 to 1874, is of prominent importance for the development of the Law of Nations. Under the aegis of the principle of nationality, Austria turns in 1867 into the dual monarchy of Austria-Hungary, and Italy as well as Germany becomes united. The unity of Italy rises out of the war of France and Sardinia against Austria in 1859, and Italy ranges henceforth among the Great Powers of Europe. The unity of Germany is the combined result of three wars: that of Austria and Prussia in 1864 against Denmark on account of Schleswig-Holstein, that of Prussia and Italy against Austria in 1866, and that of Prussia and the allied South German States against France in 1870. The defeat of France in 1870 had the consequence that Italy took possession of the Papal States, whereby the Pope disappeared from the number of governing sovereigns.
The United States of America rise through the successful termination of the Civil War in 1865 to the position of a Great Power. Several rules of maritime International Law owe their further development to this war. And the instructions concerning warfare on land, published in 1863 by the Government of the United States, represent the first step towards codification of the Laws of War. In 1864, the Geneva Convention for the amelioration of the condition of soldiers wounded in armies in the field is, on the initiation of Switzerland, concluded by nine States, and in time almost all civilised States became parties to it. In 1868, the Declaration of St. Petersburg, interdicting the employment in war of explosive balls below a certain weight, is signed by many States. Since Russia in 1870 had arbitrarily shaken off the restrictions of Article 11 of the Peace Treaty of Paris of 1856 neutralising the Black Sea, the Conference of London, which met in 1871 and was attended by the representatives of the Powers which were parties to the Peace of Paris of 1856, solemnly proclaimed "that it is an essential principle of the Law of Nations that no Power can liberate itself from the engagements of a treaty, or modify the stipulations thereof, unless with the consent of the contracting Powers by means of an amicable arrangement." The last event in this period is the Conference of Brussels of 1874 for the codification of the rules and usages of war on land. Although the signed code was never ratified, the Brussels Conference was nevertheless epoch-making, since it showed the readiness of the Powers to come to an understanding regarding such a code.