Completed in 1914, the ship performed limited neutrality patrols in the Sea of Åland and the northern reaches of the Stockholm Archipelago during the war.

She was placed in reserve in 1917 to be modified to make laying mines safer and remained in that status until the beginning of World War II in 1939 to save money.

Clas Fleming was activated for a short time that year to lay defensive minefields before she began a reconstruction that installed an early version of gas turbines, the first warship in the world to be so equipped.

In 1908 the Swedish Board of Admiralty requested funding from the King in Council for a fast minelayer able to lay mines off the enemy coast at night when the ship would be less likely to be spotted.

This was granted the following year with the proviso that the ship be powered by steam turbines and be capable of conducting scouting for the fleet.

The shipyard had successfully installed two of these systems in ships and offered to build one for Clas Fleming,[6] the world's first warship powered by gas turbines.

[7] The Navy had no funding available for experimental propulsion systems until money for design work was made available through the Social Affairs Department for unemployment relief at the shipyard in 1934.

Six of the original boilers were removed with the remaining pair retained to operate the ship's steam-powered auxiliary machinery, although they were converted to burn fuel oil.

[10] Named after the 17th-century Swedish admiral Clas Fleming, the ship was ordered from Bergsund Finnboda on 17 May 1910 at a cost of SEK 1,493,350.

Laid down at the company's shipyard in Stockholm, Clas Fleming was launched on 14 December 1912, but completion was delayed by quality-control problems with the steel used in her hull and lengthy sea trials.

The ship conducted neutrality patrols until she was reduced to reserve in late 1917 in preparation for a refit that began the following year.

[11] On 24 August 1930, the coastal defense ship Manligheten ran aground while sailing between Stockholm and Hårsfjärden in poor weather.