Already in the 9th century, Kievan Rus' had the powerful naval fleet which is proved by the successful naval Siege of Constantinople of 860 However the naval fleet was irregular and was built only for the purpose of raids. Due to several major weakness of the naval fleet and in addition destructive invasion by the Mongol Empire, later the irregular naval fleet of the Kievan Rus principalities was dissolved. Except for the Principality of Novgorod which had access to the open seas (such as the Baltic Sea and the White Sea) and also was saved from Mongol invasions. As the first and proper Russian state of the Grand Duchy of Moscow begun and also got access to open water bodies, the Golden Age of the Russian Navy began. In 1570, in order to protect Russian navigation at the Baltic Sea, Ivan the Terrible created a flotilla which existed for about a year. In the 16th century, the Tsardom of Russia fought against the Ottoman Empire to get free access to the Black Sea.