The Swedish era
Sweden lost its superpower status and its most important eastern fortresses in the wars with Russia in the first half of the 1700s. Reinforcing the defences of Finland was deemed necessary. In 1747, the Swedish parliament made a decision to build a central fortress including a naval base in Helsinki and a border fortress in Degerby, off Loviisa.
The fortification work began in the following year on the Susiluodot islands off Helsinki, the location of present-day Suomenlinna. In 1750, the fortress was named Sveaborg, rendered phonetically to Viapori in Finnish. The construction of a dry dock was launched in the fortress for building warships for the Archipelago Fleet.
The ambitious fortification plans had to be scaled down a few years after the construction began, and the resources were directed to building a sea fortress. The active phase of the Viapori fortification work ended just over 40 years after it began.
The fortress was actually never quite completed as planned, even though the original aim was to complete the construction in only four years. The Pomeranian war (1756–1763) put the construction on hold, although the battles did not extend to Viapori in the 1700s. The sea fortress had merits as a naval base in the Russo-Swedish War of 1788–1790 (‘Gustav III’s War’), but it was not involved in actual battles.
In 1808, Viapori was besieged by the Russian forces in the Russo-Swedish war. After just minor skirmishes, Commandant C.O. Cronstedt decided to surrender. The reasons for surrender remains an unsolved mystery. The surrendered sea fortress was taken over by the Russians, and a new era began for Viapori.