Between 1773 and 1790 the island of Bockholmen, now known as Kuninkaansaari, was used as a naval base by the archipelago fleet of the Swedish King Gustav III. After an inconclusive battle in 1788, the fleet was defeated by Russian warships in 1789. Then in 1790 Gustav II retaliated with a reinforced fleet, and Sweden won one of its greatest naval victories – after which the island was named Kuninkaansaari – the King’s Island.
In the 19th century, after Russia gained sovereignty over Finland, the island was fortified by Russian occupiers. In 1906 unrest preceding the Russian Revolution broke out here and on neighbouring Suomenlinna, then known as Viapori, in the form of a mutinous armed uprising. The mutineers’ luck turned when an ammunition cellar blew up on the second day of the rebellion. The explosion shattered the rocks along the shore leaving a deep cleft in the cliffs. The force of the blast was so strong that windows were broken in the Helsinki district of Kallio several kilometres away.