As a consequence, the Russian sailing fleet lost its significance and was rapidly replaced by steamboats, including the first steel armored gunship "Opyt" and one of the first seafaring ironclads "Pyotr Velikiy". On 16 January 1877 Admiral Stepan Makarov became the first to launch torpedoes from a boat in combat. He also proposed the idea and oversaw the construction of the world's first ocean-going icebreaker "Yermak", commanding it in two Arctic expeditions in 1899 and 1901. At about the same time, Aleksey Krylov elaborated the modern floodability theory.