 Complete the following phrase:  In 1917, Isakov moved to Petrograd and entered the Naval Guards School of the Imperial Russian Navy and graduated as a midshipman in March of that year. He briefly saw action against the Germans in West Estonian archipelago Moonsund archipelago. He continued his service after the October Revolution in the Baltic Sea fleet as a torpedo officer, where he served on several warships, including the Izyaslav, the Riga, the Kobchik and the Korshun. In 1918, he took part in several battles against the German Imperial Navy until the signing of the Treaty of Brest-Litovsk, which effectively ended the war between Russia and Germany, granting the Baltic Sea to the latter. In March 1918, Isakov participated in the 