santahamina was the largest single island in krepost sveaborg, and is located south of laajasalo. because of the size of the island santahamina could be considered to belong to both main line of defence and the second line of defence. santahamina was fortified during the crimean war, and several gun batteries were built on the island during the decades between crimean war and first world war. most of the older guns, including eleven 6 inch 190 pood siege guns and thirteen 9 inch coastal mortars, were transported to the land front of the fortress shortly after the start of war. the remaining batteries were a 6-inch canet battery, originally intended for isosaari, at itäniemi on the south-eastern part of the island and a 75 mm battery on the eastern shore. these batteries covered the sea east of isosaari. santahamina had a large garrison area and a substantial number of troops and supplies were located on the island.