The GMSA was formed on 21 June 1945 under allied supervision, specifically that of the Royal Navy, to clear naval mines in the North Sea and Baltic. It was made up of 27,000 former members of the Kriegsmarine on nearly 300 vessels. The service was sub-divided into six mine sweeping divisions (German: Räumbootdivisionen). The German headquarters of the service were located in Glückstadt. On 25 May 1946, the GMSA was equipped with new blue work uniforms and special rank insignia, worn on the sleeve.