Krepost Sveaborg - Naval Front

Naval Front

Coastal fortifications on the naval front protected Krepost Sveaborg from an attack from the sea. During the war new fortifications were built on the outlying islands pushing the defences outward to protect the ships in the harbour from new modern guns. During the First World War the naval front of the fortress was modernized almost completely. The new gun batteries can be divided into four types: heavy long range batteries, close range batteries, anti-landing batteries equipped with field guns and anti-aircraft batteries which appeared during the war for the first time. The naval front was divided into six sectors at the start of the war with sectors 1-4 comprising the old fortress, sector 5 Isosaari and sector 6 Melkki. The central fire control post was located in Vallisaari. As the new coastal forts were completed the organization changed and the naval front was divided into two parts: an outer main line of defence from Melkki to Isosaari and an inner second line of defence from Lauttasaari to Santahamina. The naval front command post was located in Vallisaari and the main artillery command post in Kuivasaari.

The long range batteries of 10 in (254 mm) and 6 in (152 mm) guns included ten batteries with six 10 inch batteries and four 6 inch batteries, with one more under construction. The basic shape of the batteries is four guns in a row protected from the front by a concrete parapet of approximately 5 m (16 ft) thick with traversal walls between the gun positions. The batteries had no rear protection. Shelter for crew and ammunition cellars were built into and under the front parapet and the traversal walls. While the basic plan is similar, each battery is unique depending on the terrain. For the 10 inch guns the average distance between guns is 40 m (131 ft), but on smaller island such as Katajaluoto the guns are only 30 m (98 ft) apart while the larger Isosaari battery (No 1) has guns 50 m (164 ft) apart. Similarly the 6 inch batteries have guns 35 m (115 ft) apart on average, but in the very cramped Harmaja battery the distance between guns is only 20 m (66 ft) and the battery is not built on straight line but in a crooked L-shape. Many batteries have an icon closet framed with granite.