The Black Sea Fleet is considered to have been founded by Prince Potemkin on May 13, 1783, together with its principal base, the city of Sevastopol. Formerly commanded by such legendary admirals as Dmitriy Senyavin and Pavel Nakhimov, it is a fleet of enormous historical and political importance for Russia. In 1790, Russian naval forces under the command of Admiral Fyodor Ushakov defeated the Turkish fleet at the Battle of Kerch Strait. From 1841 onward, the fleet was confined to the Black Sea by the London Straits Convention. As a result of the Crimean War, one provision of the Treaty of Paris was that the Black Sea was to be a demilitarized zone like the Island of Åland in the Baltic Sea, although Russia subsequently renounced the treaty and reconstituted its naval strength and fortifications in the Black Sea. The crew of the battleship Potemkin revolted in 1905 soon after the Navy's defeat in the Russo-Japanese War. Lenin wrote that the Potemkin uprising had had a huge importance in terms of being the first attempt at creating the nucleus of a revolutionary army. During World War I, there were a number of encounters between the Russian and Ottoman navies in the Black Sea. The Ottomans initially had the advantage due to their having under their command the German battlecruiser SMS Goeben, but after the two modern Russian dreadnoughts Imperatritsa Mariya and Imperatritsa Ekaterina Velikaya had been built in Mykolaiv, the Russians took command of the sea until the Russian government collapsed in November 1917. German submarines of the Constantinople Flotilla and Turkish light forces would continue to raid and harass Russian shipping until the war's end.
Question: What two seas were demilitarized?
Answer: Black Sea | Baltic Sea