[2] As the threat of war in Europe became ever more clear the decision was made to improve the Royal Norwegian Navy's mine warfare capabilities.

At first a number of 2. class gunboats were rebuilt into minelayers and mine sweepers, but with war looming it soon became clear that more capable vessels were required.

In response to this report, the Norwegian government ordered the minesweepers Otra and Rauma to sail north from their base in Horten and sweep the minefields on 9 April 1940.

[5] While her sister ship, HNoMS Rauma, was fighting the German naval forces in Horten Otra was cut off and isolated from the action.

[2][8] On 18 January 1946 Togo was returned to the Royal Norwegian Navy at Bogen and on 30 October 1946 was renamed HNoMS Otra.