Krepost Sveaborg
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.
Background
had ceded Grand Duchy of Finland to Russian Empire as the result of the Finnish War of 1808—1809 and along with it the fortress of Sveaborg, Viapori, the present day Suomenlinna. The fortress protected the southern Finland and became a naval base for the Russian Baltic Fleet. After the end of the Napoleonic Wars many new buildings were built to improve the living conditions on the fortress, but the fortifications were neglected. After the start of the Crimean War in 1853 construction of new fortifications began on the other nearby islands and on the southern shore of Helsinki peninsula. In 1854 an Anglo-French naval fleet entered the Baltic Sea, hastening the work. These fortifications protected the flanks of the fortress and provided depth to the defence, but the problem of obsolescent artillery was not solved. Thus when the fleet attacked the fortress on the 6th of August 1855 they were able to bombard the fortress for two days from a distance of while the best Russian guns had a maximum range of.After Crimean War fortifications of Viapori were improved by building artillery casemates and new bomb-proof buildings. Vallisaari just east of Suomenlinna was the site of the first new construction works. The harsh suppression of the Polish January Uprising of 1863 and the resulting criticism soured the relationships between Russia and western Europe and hastened the fortification works. Between 1863 and 1864 redoubts were built on Vallisaari, Kuninkaansaari and Santahamina islands. In 1860s and 1870s Russia purchased and then built under license new Prussian Krupp rifled breech loading guns which were also used in Viapori. A total of 32 new bomb-proof stone powder cellars were built by the beginning of the 1870s, further improving the defences. The Russo-Turkish War of 1877–1878 was the next crisis that threatened the peace between Russia and England, with new batteries being built at Viapori on Kuninkaansaari and older ones improved or rebuilt. New technology in the form of telegraph, railway lines and searchlights began to be used. Improvements in artillery and ammunition forced improving the gun positions by covering the old walls and fortifications with a thick earthen walls. With high-explosive shells appearing at the end of the 19th century earth and stone were no longer sufficient and first concrete fortifications with steel doors were built in Viapori. Continually improving guns resulted increased range, necessitating rangefinders, while heavier guns and ammunition required improving piers, roads, cranes and ammunition carts to transport the guns or move ammunition from magazines to guns. Despite the improvements the funds and resources allocated to the fortress were not sufficient to keep pace with the evolution of military technology. While parts of the fortress or were improved and new weapons or equipment were received, the overall condition of the fortress became ever more obsolescent, and the vulnerability of the flanks and rear were a lasting problem. By the end of 1880s and early 1890s Viapori could no longer be considered a proper fortress but only a coastal position, capable of defending only against an enemy coming directly from the sea. The primary role of the fortress became more one of internal politics, as it helped the Russians maintain control of Helsinki.
Krepost Sveaborg
In the 1890s the priority of the fortification works in the Baltic Sea had been the protection of the ice-free port of Liepāja, and the Kronstadt fortress protecting Saint Petersburg, relegating Viapori to a secondary status. After the losses during the Russo-Japanese War and in light of the rising might of the Imperial German Navy, Liepāja was considered too vulnerable for a main fleet base, and the decision to build Peter the Great's Naval Fortress was made. In the new plans the main line of defence against the enemy was at the Porkkala-Tallinn line with Tallinn also the new main base for the Russian Baltic Fleet. Helsinki was to be a base for torpedo boat flotillas. The construction of the Tallinn naval base was delayed however, and with the new ships being constructed to replace the losses suffered against Japan the Russian Navy was forced to rely more on Helsinki despite the obsolete armament and inadequate fortifications at Viapori. As the threat of war in Europe grew, it became essential to expand the fortress to provide a necessary protection for the naval base. Until 1910, when the first 152 mm Canet guns arrived, the only modern weapons at Viapori were 57 mm quick fire guns with the rest of the artillery designs dating from the Russo-Turkish War. The first new 254 mm guns arrived in 1913, but it was not until early 1914 that construction of the first new batteries began on Melkki and Isosaari. During the First World War the new Krepost Sveaborg was built to substantially expand the old fortress. A new main line of defence was constructed on the outlying islands, pushing the defensive line several kilometers southward, thus providing a secure outer anchorage south of the old fortress for larger warships without the need to navigate the narrow straits leading to the inner anchorage at Kruunuvuorenselkä. The older parts of the fortress became a second line of defence and the main storage areas. The rear of the fortress was finally protected by land fortifications, at first field fortifications on the Helsinki peninsula built in 1914, and, later, an outer line of fixed fortifications.Troops and organization
At the start of the First World War Krepost Sveaborg was subordinated to the Russian 6th Army. In summer 1916 Krepost Sveaborg was subordinated to Baltic Fleet. At the start of the war Krepost Sveaborg was divided into three defensive areas, with the sea front forming one defensive area and the land front divided to Pasila and Laajasalo-Herttoniemi areas. The sea front was further divided into six sectors, with sectors 1–4 at the old fortress, sector 5 at Melkki and sector 6 at Isosaari. The sea front was divided into main line of defence from Melkki to Isosaari and second line of defence from Lauttasaari to Santahamina at the end of 1914. As the new batteries were constructed Melkki was relegated to second line of defence and Lauttasaari to land front in spring 1915. At the land front new defensive lines were constructed from 1915 onward further away from the city center. The new land front was divided into three sectors: eastern, northern and western. Krepost Sveaborg was also responsible for a larger fortification district that included coast line west of the fortress until Hanko.At the start of the war the fortification artillery units manning the fortress were organized into nine artillery companies and a machine gun detachment. In April 1915 the fortification artillery units were reorganized into a single fortification artillery regiment with three battalions and a machine gun company. Four companies manned the coastal forts at sea front. In June 1916 the regiment was divided in two, with 1st regiment responsible for the seaward defence and the 2nd for the landward defence. Both regiments had ten companies in three battalions. The 1st regiment was divided into three defence detachments, with south-western and south-eastern detachments responsible for the main line of defence on the outlying islands with the newest guns, while the third detachment manned the second line on the old fortress. The artillery regiments had a common supply unit responsible for the weapons, ammunition, transportation between islands etc. A signals company built and maintained the communication lines. The minefields around the fortress were built by the Krepost Sveaborg mine company, from 1915 a mine battalion. In 1916 the fortress was reinforced by the mine battalion from Vladivostok fortress. Construction and engineering department of the fortress headquarters organized the construction works of the fortress with engineering and sapper units as well as the civilian workers.
Infantry units at the fortress manned the landward defences and provided detachments on the coastal forts for anti-landing and close defence duties. The peacetime Krepost Sveaborg fortress infantry regiment was reinforced by conscript units, which in 1915 were organized as the 427th and 428th infantry regiments to a new 107th infantry division which was sent to front line after a training period. In spring 1916 regiments from the new 116th division manned the fortress. At the autumn of 1916 units from different fortresses were brought to Krepost Sveaborg and organized into the 128th infantry division. In July 1917 the fortress was manned by the fortress infantry regiment and the 428th Lodeynoye Pole infantry regiment of the 128th division. In October 1917 the 128th was replaced by the 29th infantry division, badly mauled at the front and brought to Krepost Sveaborg for rest. At January–February 1918, when Finland gained its independence, Krepost Sveaborg had six infantry regiments: the 696th revolutionary regiment, the fortress infantry regiment and 113th, 114th, 115th and 116th regiments of the 29th infantry division.
Construction workers included Russian soldiers but also Finnish civilian workers and forced labour using prisoners transported from far east. Finns were exempt from conscription, and thus there was available manpower for fortification works. The payment for fortification works was slightly above average for manual labour, and made it an attractive option particularly for many rural workers. In 1915 when large scale construction of fortifications around Finland began Russians instituted a work responsibility for Finns based on wartime emergency law to obtain the necessary labour force. To ease the manpower shortage Russians brought convicted prisoners from far east to Finland in summer 1916 as forced labour. Approximately 2000-3000 men, including Chinese, Kyrgyz and Tatars, were employed as lumberjacks around Espoo and Sipoo. Kyrgyz were mainly guards. Asian workers were transported back to Russia already in 1917 however, citing the workers to be unaccustomed to the northern climate and possible threat of rebellion. The total number of workers in not known, but an estimated 10 000 to 15 000 men were used in construction works around Helsinki and up to 100 000 total in Finland. Complicated bureaucracy delayed the construction works, and the supervision of the works was also poor, leading to a widespread graft.
Armament
Coastal guns
The most powerful coastal guns used at Krepost Sveaborg were the 45 caliber model 1891 guns. They had a maximum range of but suffered from primitive mountings: the heavy guns, weighing, were completely hand-operated resulting in slow traverse and elevation rates and exhausting the gun crews. The rate of fire was only one shot every two minutes and they were also not capable of penetrating the armour of newer warships: at the range of they could penetrate of armour at 90° angle. First four guns were transported to the fortress in 1913 from Kronstadt fortress, two guns each from Constantin and Obrutshev forts. Twelve guns were transported from Vladivostok in 1914 and eight more arrived in 1915, with a total of 24 guns in six four-gun batteries. These guns formed the primary armament of the sea front main line of defence. The batteries were located on Rysäkari, Katajaluoto, Kuivasaari, Isosaari and Itä-Villinki.The 45 caliber model 1892 guns supplemented the 10 inch guns of the sea front main line of defence. These guns were French Canet guns and had a maximum range of. Unlike the 10 inch guns, the 6 inch guns had a modern counter-recoil system and achieved a rate of fire of five shots per minute. The six inch guns were intended against destroyers and other smaller vessels. They were installed in four batteries of four guns each at the sea front on Miessaari, Harmaja, Isosaari and Santahamina. A fifth battery was under construction on the mainland at Skatanniemi cape. The guns for this battery arrived, bringing the total sea front number to twenty, but the construction was not completed before the war ended. Further seventeen guns on lower ship deck mountings with lower maximum elevation were used on the land front. The guns used at Krepost Sveaborg included both Russian Obukhov licence-produced guns and French Schneider guns.
The older heavy coastal artillery pieces, the and model 1867 and 1877 guns and the 9-inch mortar M1877| and 11-inch mortar M1877| model 1877 coastal mortars, were mostly transferred to land front or placed in reserve. Three batteries of 11 inch model 1877 guns were used throughout the war at the sea front second line of defence at Kustaanmiekka, Kuninkaansaari and Vallisaari. At the start of the war 11 inch guns were also used at the main line of defence on Isosaari before 10 inch model 1891 guns replaced them. Two batteries of 11 inch coastal mortars remained in use until 1916 in Vallisaari and Kuninkaansaari. The mortars were also capable of firing to the rear of the fortress and were intended to keep the citizens of Helsinki loyal. The heavy shells of the mortars were considered to have a "suitable moral effect" on civilians. 22 caliber siege gun model 1877 was primarily an army weapon used on wheeled carriage on land front, but some guns mounted on fortification mounts were also used on sea front at the start of the war.
Light coastal guns used at Krepost Sveaborg included 57 mm Nordenfelt guns, fifteen guns at the beginning of the war and twenty by the end of the war. 50 caliber model 1892 Canet guns were similar to the six inch model 1892 gun. First of these guns arrived at 1914, and twelve coastal guns were used at Krepost Sveaborg, with another eighth anti-aircraft gun versions with a 50° maximum elevation.
It was planned in 1916 to build four two-gun batteries of 52 caliber model 1907 guns at Krepost Sveaborg, but the work started in 1917 never progressed beyond building gun mount foundations and some ammunition and crew shelters. The batteries were to be built on the mainland, with guns in single open positions capable of firing on both land and sea targets. The batteries were located at Munkkiniemi, Haaga, Oulunkylä and Koskela. The 305 mm guns were used later to protect Helsinki however, as Finland built an armoured twin turret on Kuivasaari between 1931 and 1935 and two guns in open positions at Isosaari during the Second World War in 1941–1944.
Field guns
Field guns were used on both the land front and as anti-landing and close defence weapons on the coastal forts. Gun models included both older fixed carriage guns and more modern weapons with counter-recoil systems. The most common models were the 6 inch siege gun model 1877 with a 190 pood version used on both field and fortress mounts and a lighter 120 pood barrel version on field carriage. 42 line battery gun model 1877 and 34 line light field gun model 1877 were other older field artillery pieces used at the fortress. 76 mm model 1902 gun was a newer rapid fire field gun with a counter recoil system. The 76 mm model 1902 gun was also used as an anti-aircraft gun on a modified "Rosenberg" mount. The land front weaponry also included a variety of smaller caliber anti-storming guns, caponier guns and other mixed artillery pieces. The reserve guns included different older models up to bronze-barrelled mortars.Mines
s were also used to protect Krepost Sveaborg from an attack from the sea. An outer line of contact mines was laid approximately outside the main line of defence. Shore detonated controlled mines were used to create an inner mine barrier to protect the entrances to the outer anchorage. These mines were laid typically in three rows with separation between rows and between mines in a row. Controlled mines required an extensive cabling system to the shore stations where the command to detonate the mines was given. Fortified electrical stations provided the necessary electricity for the mine control network. Electricity was also used for communication systems, searchlights, electrical ammunition lifts and in barracks and crew shelters.Equipment
Rangefinders
, where the known base length is the height of the rangefinder from sea level, were first used at Viapori in the 1880s. Vertical based rangefinders required only one instrument, but they were susceptible to interference from vibration caused by firing of the guns. Vertical based rangefinders also required a substantially high measurement site that was a problem on the low islands. To measure distance with reasonable accuracy to a target away the rangefinder had to be at least 10 fathoms and preferably 20 fathoms high - often impossible to achieve. Measurement sites had usually the rangefinder on a stone or masonry column high lying on a granite foundation. The measurement pavilions had simple wooden walls and sheet metal roof protecting them from the elements and were in size. Vertical rangefinders were no longer used on the new forts built on the outer islands.Distance measurement at the model 1891 batteries was based on horizontal triangulation from two different points, a primary and secondary, on separate islands. The rangefinders used were general von der Launitz's models 1903 and 1905–07. The average distance between the two points at Krepost Sveaborg was. Target information was sent from the primary point to the battery command point. If the primary point was located away from the battery or directing a different battery a rangefinder converter designed by colonel Kovanko was used to calculate the firing solution. A weakness in using two measurement points was that any malfunctions in either of the rangefinders or in the telephone system would render the system inoperable. Target indication between the primary and secondary points could also pose problems, as there would often be several similar target ships. The system was also not capable of measuring distances to targets in the rear of the battery; a maximum measurement sector was 140°.
On the smaller model 1892 Canet gun and anti-aircraft batteries wide Zeiss stereoscopic rangefinders were used. Maximum distance that could be reliably measured with three meter rangefinders was, while the maximum range of the six inch guns was. A single rangefinder was used by the commander of the artillery in a central fire control station at Kuivasaari. Six meter rangefinders were also planned for the 10 inch batteries later in the war but never obtained.
Searchlights
Searchlights were first used at Viapori during the Russo-Turkish War in 1878, and they were originally intended for guarding the controlled mine barriers. During the First World War fortified searchlight positions were part of the coastal forts. The main line of defence had larger two searchlights at Rysäkari and Kuivasaari and an additional six smaller searchlights beside them and on the other islands. Miessaari 150 cm searchlight position was not completed during the war. In the second line 150 cm searchlights were used on Kuninkaansaari and Vallisaari, while other forts had or searchlights. Diesel generators provided the necessary electrical power to operate the searchlights. Searchlights were used in disappearing positions, where the searchlight was normally in a shelter and only exposed when needed for illumination. The disappearing positions had two types: either the searchlight was raised from the shelter by a lifting mechanism, or it was moved by rails from the shelter to position.Communications
Telephone and telegraph system linked the various parts of the fortress. Krepost Sveaborg had both a regular telephone system and a second, independent telephone network dedicated for fire control. The primary telephone exchange was located on Iso Mustasaari. The various island forts had their own telephone exchanges, while Kuivasaari and Isosaari had central coastal telephone exchanges with links to other main line of defence forts. The telephone cabels on main line of defence were usually buried, while second line used overhead lines. Besides telephone optical telegraphs, signal lamps and signal flags were also used.Land front
To protect Krepost Sveaborg and the naval base in particular from a German attack from land the fortifications were built to protect the fortress. The first fortifications were hastily built in 1914 to block access to the Helsinki peninsula and to guard the eastern flank of Laajasalo and Santahamina by a scarce line of fortifications at Ruskeasuo-Pasila-Käpylä-Koskela-Viikki-Herttoniemi-Roihuvuori. Lauttasaari, Meilahti and Laajasalo were also fortified to some extent. It was also planned to fortify Kulosaari and Vartiosaari. These first fortifications were field fortifications located from the city center, with the defence concentrated at fortified hilltop redoubts.In early 1915 it was decided to build new defenses further away from the city center. The new defenses were stronger fixed fortifications with positions quarried into rock or dug into ground. Fortifications were built from wood and stone masonry as well as concrete. New fortifications had a network of defensive structures, with trenches, rifle pits, machine gun nests, barbed wire obstacles, shelters and roads. Artillery batteries were located behind the front line, often located on reverse slope. Artillery batteries had 2–6, typically four, guns. Heavily fortified caponiers providing flanking fire were built on places of the front line. First a northern line was built at Leppävaara-Kaarela-Pakila-Pukinmäki-Myllypuro-Vartiokylä. Construction on a western line from Leppävaara to Westend via Tapiola began shortly afterwards. In late 1915 it was decided to build an outer line of defence on the northern and eastern sectors, extending the fortifications northward and in the east from Pukinmäki to Malmi, Mellunkylä and Vuosaari. Fortification works continued until the February revolution of 1917, and some work was done until early 1918. The land front was divided into three sectors, eastern, northern and western with 36 bases, numbered I-XXXVII. The bases were usually centered on hilltops with the strongest defences.
The basic front line fortifications were open or covered machine gun nests, rifle pits, observation posts and shelters. Most of the structures were designed to be covered with a concrete roof poured on wooden planks occasionally reinforced with railway tracks. Some of the positions were built with stone or logs. Many of the fortifications have been left uncovered however, built only to a point where adding the missing roof could be accomplished quickly. The basic fortified types are a type A square machine gun nest, type B square rifle or machine gun pit, type C rounded rifle or observation pit, type D oval rifle pit with several firing ports and types E and F large rifle positions for multiple shooters. There is considerable variation between individual structures among the basic types, with newer positions generally built larger and stronger.
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 and 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 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, but on smaller island such as Katajaluoto the guns are only apart while the larger Isosaari battery has guns apart. Similarly the 6 inch batteries have guns apart on average, but in the very cramped Harmaja battery the distance between guns is only and the battery is not built on straight line but in a crooked L-shape. Many batteries have an icon closet framed with granite.