the krepost sveaborg was an imperial russian system of land and coastal fortifications constructed around helsinki during the first world war. the purpose of the fortress was to provide a secure naval base for the russian baltic fleet and to protect helsinki and block routes to saint petersburg from a possible german invasion. krepost sveaborg was part of peter the great's naval fortress, a coastal fortification system protecting access to saint petersburg by sea. the central part of krepost sveaborg was the old fortress of suomenlinna where the fortress headquarters were located. due to technological advances in artillery the old fortress was no longer capable of providing a sufficient protection, and a new main defensive line was built well beyond the old fortress boundaries. new coastal artillery guns built on outlying islands protected krepost sveaborg from the sea, while fortified lines constructed around helsinki were intended to stop any attacks on land. the primary coastal guns were model 1891 guns and model 1892 canet guns. older model 1877 guns were also used. in summer 1917 the fortress had two hundred coastal or anti-landing guns, of which 24 were 10-inch guns in six batteries, 16 were 6-inch canet guns in four batteries and twelve were 11-inch guns in three batteries. the artillery used in land fortifications included older coastal guns, old fixed carriage guns and newer light field guns. in march 1917, krepost sveaborg had a total of 463 guns, although many of them were obsolescent. krepost sveaborg was still partly incomplete in 1917 when the february revolution halted most of the construction work. some further construction work was carried out during the remaining year, but all work halted during the october revolution. following the finnish declaration of independence, parts of the land fortifications were used in the finnish civil war. the coastal fortifications were later taken over by finland to protect helsinki, while the land fortifications were mostly abandoned and disarmed.