 Complete the following phrase:  The surviving sisters were modified to lay mines shortly after the war began. They laid mines themselves during the war and provided cover for other ships laying minefields. Admiral Makarov and Bayan fought several inconclusive battles with German ships during the war, including the Battle of Åland Islands in mid1915, and they also defended Moon Sound during the German invasion of the Estonian islands in late 1917, where Bayan was badly damaged. Their 75 mm guns were removed in 19161917 and replaced by one 8-inch and four 6-inch guns. A pair of anti-aircraft guns were also added. Admiral Makarov was in Helsingfors when Finland declared independence in March 1918, and was forced to evacuate even though the Gulf of Finland was still frozen over. She reached Kronstadt after what became known as the 