Suomenlinna (Swedish: Sveaborg) is an inhabited sea fortress built on six islands within city limits of Helsinki, Finland. It is a UNESCO World Heritage site and popular with both tourists and locals, who enjoy it as a picturesque picnic site.
Sweden started building the fortress in 1748 as a protection against Russian expansionism. The general responsibility for the job of fortification was given to Augustin Ehrenswärd. The original plan was strongly influenced by the precepts of Vauban, the foremost military engineer of the time.
In addition to the island fortress itself, seafacing fortifications on the continent would ensure that an enemy could not get a beach-head there from which to attack. The plan was also to stock munitions for the whole Finnish contingent of Swedens army and navy there.
In the Finnish War the fortress surrendered to Russia in 1808, paving the way for a Russian occupation of Finland in 1809.
Sweden started the building of Suomenlinna in 1748, when Finland was still a part of the Swedish kingdom. Augustin Ehrensvärd (1710-1772) and his gigantic fortification work on the islands off the town brought the district a new and unexpected importance.
In 1703 Peter the Great founded his new capital, St. Petersburg, in the furthest-flung corner of the Gulf of Finland. In the approach to it he built the fortified naval base of Kronstadt. Russia had become a maritime power and a force to be reckoned with in the Baltic.
The situation posed a threat to Sweden; Russian naval units made skirmishes right up to the Swedish coast. Other European states were also concerned about developments, especially France, with which Sweden had concluded a military alliance. After lengthy debate the Swedish diet decided in 1747 to fortify the Russian frontier and to establish a naval base at Helsinki as a counter to Kronstadt. The frontier fortifications were established at Loviisa.
Fortification of Helsinki and its islands began in January 1748, when a young Swedish lieutenant colonel by the name of Augustin Ehrensvard came to Finland to direct the operations. A number of fortifications were also built on the Russian side of the new border during the 18th century and some of the existing Swedish ones were added to.
Following a pact between Alexander I and Napoleon, Russia occupied Finland in 1808. By the Treaty of Hamina in 1809 Finland became an autonomous duchy within the Russian Empire. The Swedish period in Finnish history, which had lasted over 600 years, had come to an end.
The long period of peace following the transfer of power was shattered by the Crimean War of 1854-56. The allies decided to engage Russia on two fronts and sent an Anglo-French fleet to the Baltic. For two summers the fleet shelled the towns and fortifications along the Finnish coast. Bombardment of Suomenlinna (then known as Sveaborg or Viapori) lasted three days and the fortress was badly damaged.
After the Crimean War extensive restoration work was begun at Suomenlinna. A new ring of earthworks with artillery emplacements was built at the western and southern edges of the islands.
The next stage in the arming of Suomenlinna and the Gulf of Finland came in the build-up to the First World War. Suomenlinna and its surrounding islands became part of "Peter the Great's naval fortification" designed to safeguard the capital, St. Petersburg. The fortress during the Swedish era
The fortress under the Russian rule