Sweden 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, , 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 .