The Russo-Turkish Wars of Catherine the Great resulted in the establishment of the Black Sea Fleet, with its bases in Sevastopol (1783) and Kherson. It was at that time that Russian warships started to venture into the Mediterranean on a regular basis. In 1770, Grigoriy Spiridov's squadron gained supremacy in the Aegean Sea by destroying the Turkish fleet in the Battle of Chesma. After having advanced to the Danube, the Russians formed the Danube Military Flotilla for the purpose of guarding the Danube estuary from the Turks and they came in 1771 as guests to Dubrovnik in the Republic of Ragusa. The Beluga caviar from the Danube was famous and the merchants from the Republic of Ragusa dominated the import-export business in Serbia with the Habsburg Monarchy. The Russian Navy captured in 1780 two British cargo vessels, their cargo were hemp and iron. The Republic of Ragusa became one of the chief carriers of the Mediterranean in 1783 with the help of the U.S., when Britain acknowledges the United States independence, although the Americans agreed to allow Dubrovnik's ships free passage in their ports.