The coastal artillery had a range of about 25 km (16 mi)[citation needed] and could thus "close" the gap between the shores, trapping enemy ships in a crossfire.

The decision to start construction of the naval fortress line came after the disastrous events at Tsushima, where the whole Russian Baltic Fleet had been annihilated.

The quickest and cheapest way of dealing with this problem was to protect Saint Petersburg with a seemingly impenetrable zone of coastal artillery until a new fleet had been constructed.

In April 1918, following a request from the Senate of Vaasa in Finland, the German Ostsee Division, led by Rüdiger von der Goltz, landed in Hankoo, joined the Finnish Whites in the fight against the Reds, and conquered Helsinki.

In the 1930s, the Finnish and Estonian coastal defenses made extensive plans to use the fortresses against their former masters, and prevent the Soviet Baltic Fleet from gaining access to the seas.