The sea fort of Nya Älvsborg

Nya Älvsborg, called to distinguish it from the earlier fortress at Old Älvsborg, is a sea fort on the island of Kyrkogårdsholmen within the urban area of modern Gothenburg, Sweden. Construction began in 1653 to protect what was at the time Sweden's only access to the North Sea and the Atlantic Ocean. The fortress remained in service until 1869, though it only saw significant action in one conflict, the Great Northern War.

During the Great Northern War, the Danish-Norwegian captain Peter Tordenskjold sought to hamper Swedish naval forces based at Gothenburg. On July 19 and 20, 1719, Tordenskjold gathered his forces in the Gothenburg Archipelago to make a direct assault on Nya Älvsborg. The fortress had a garrison of around 360 men under the command of Johan Abraham Lillie. The Swedish artillery amounted to around 90 pieces, including mortars and howitzers.

From the Aspholmar, Danish-Norwegian artillery subjected Nya Älvsborg to heavy bombardment. The fortress suffered continuous fire for three days without pause, causing significant damage. Lillie refused to surrender, responding to calls for surrender by stating he would rather be brought back to Gothenburg as a dead Lillie than as a living Danckwardt.

Under the resulting Treaty of Roskilde, the Norwegian province of Bohuslen and the Danish province of Halland were both ceded to Sweden, which made the Göta Älv estuary - and thus by extension both Nya Älvsborg and Gothenburg - much less vulnerable to Danish-Norwegian attacks. By the 18th century, the defenses at Nya Älvsborg were increasingly neglected. When King Gustav IV Adolf visited in 1801, he found the fortress to be in a state of disrepair.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons