as the Norwegian-Dutch Cornelius Cruys, the Greek Ivan Botsis, or the Scotsman Thomas Gordon. In 1718, the Admiralty Board (Адмиралтейств-коллегия) was established as the highest naval authority in Russia. The organizational principles of the Russian Navy, educational and training methods for preparing future staff, and methods for conducting military action were all summarized in the Naval Charter (1720), written by Peter I himself. Peter the Great, Feodor Apraksin, Alexey Senyavin, Naum Senyavin, Admiral Mikhail Golitsyn and others are generally credited for the development of the Russian art of naval warfare. The main principles of naval warfare were further developed by Grigory Spiridov, Feodor Ushakov, and Dmitry Senyavin. Between 1688 and 1725, a period spanning most of Peter's reign, some 1,260 seagoing vessels were built in Russian shipyards for the Imperial Russian Navy. Fleets were launched successively on the White Sea, the Sea of Azov (with access to the Black Sea), the Baltic Sea, and the Caspian Sea (Russo-Persian War of 1722-1723). In 1700, the majority of sailors in the Imperial Russian Navy were foreigners at the start of the Great Northern War. But by 1721, at the end of the same war, the navy had 7,215 native-born sailors. 18th century In the second half of the 18th century, the Russian Navy was built up to support the government's foreign policy. The nation conducted the Russo-Turkish wars for supremacy in the Black Sea. For the first time, Russia sent its squadrons from the Baltic Sea to distant theaters of operations (see Archipelago expeditions of the Russian Navy). Admiral Spiridov's squadron gained supremacy in the Aegean Sea by destroying the Turkish fleet in the Battle of Chesma in 1770. In 1771, the Russian army conquered the coasts of the Kerch Strait and fortresses of Kerch and Yenikale. After having advanced to the Danube, the Russians formed the Danube Military Flotilla for the purpose of guarding the Danube estuary. In 1771 they were guests to the Republic of Ragusa. The Beluga caviar from the Danube was famous, and merchants from the Republic of Ragusa dominated the import-export business in Serbia with the Habsburg monarchy. In 1773 the vessels of the Azov Flotilla (created anew in 1771) sailed into the Black Sea. Russia defeated Turkey in the Russo-Turkish War of 1768–1774, gaining control of the Sea of Azov and a part of the Black Sea coastline between the rivers Bug and Dniester. The Crimea