The restriction imposed on the Black Sea Fleet by Turkish control of the Straits was influential in motivating Russia from time-to-time to attempt to secure control of the passage, which became a recurrent theme in Russian policy. From 1841 onward the Russian fleet was formally confined to the Black Sea by the London Straits Convention. However, within the Black Sea itself, the Turks found themselves at a naval disadvantage in relation to the Russian Black Sea Fleet. In 1853, the Black Sea Fleet destroyed Turkish naval forces at the Battle of Sinop after the Turks had declared war on Russia. Nevertheless during the ensuing Crimean War, the Russians were placed on the defensive and the allies were able to land their forces in Crimea and, ultimately, capture Sevastopol.