vasikkasaari was used as a fuel and ammunition depot of krepost sveaborg. the island is located in kruunuvuorenselkä where the inner anchorage of the fortress was, between suomenlinna, santahamina and laajasalo. three large fuel oil tanks served the naval base and two smaller diesel tanks provided fuel for the mine company (later battalion) ships of the fortress. a pumping station powered by steam engine was connected to the tanks. eight storage magazines housed weapons, ammunition, mines and torpedoes with a narrow gauge railway built on the island connecting them to the main pier. at the start of the war a 57 mm quick fire battery was located on the island, replaced by a 75 mm anti-aircraft battery in spring 1915. the anti-aircraft battery was relocated in summer 1916. a 90 cm searchlight was also located on the island.