The M class were the standard minesweeper

Minesweeper (ship)

A minesweeper is a small naval warship designed to counter the threat posed by naval mines. Minesweepers generally detect then neutralize mines in advance of other naval operations.-History:...

  of the German Navy (Kriegsmarine

Kriegsmarine

The Kriegsmarine was the name of the German Navy during the Nazi regime . It superseded the Kaiserliche Marine of World War I and the post-war Reichsmarine. The Kriegsmarine was one of three official branches of the Wehrmacht, the unified armed forces of Nazi Germany.The Kriegsmarine grew rapidly...

) during World War II.

M1935

The first series; the M1935 were ordered in the late 1930s to replace worn out World War I vintage boats. These ships proved versatile and seaworthy. The vessels could also undertake convoy escort, anti-submarine warfare and minelaying tasks as well as minesweeping. However the ships were very expensive and complicated to build, and their oil fired boilers, meant they suffered from the fuel shortages in the later years of the war. A total of 69 ships were built in eight different shipyards, between 1937 and 1941. 34 were lost during the war.

M1940

Although the M1935 was a very satisfactory vessel, it was complex and expensive to build and a simplified design was put into production in 1941. These ships had coal-fired boilers because of oil shortages. A total of 127 ships were built between 1941 and 1944, and 63 M1940 class ships were sunk during the war.

M1943

This was a further simplified and slightly enlarged version of the M1940. These ships were designed for pre-fabrication and were produced in four versions:

• Minesweeper
• Anti-submarine vessel with extra depth charges
• Torpedo boat, with two 533 mm (21 in) torpedo tube
  Torpedo tube
  A torpedo tube is a device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units installed aboard surface vessels...
  
  s
• Torpedo training vessel

Only 18 vessels were completed by the time the war ended.

Post-war

After the end of the war the surviving ships allocated to the United States, Britain and the Soviet Union.
Many were assigned to the German Mine Sweeping Administration

German Mine Sweeping Administration

The German Mine Sweeping Administration was formed from former crews and vessels of the Nazi German Kriegsmarine for the purpose of mine sweeping after the Second World War, predominantly in the North Sea and Baltic Sea, and existed from June 1945 to January 1948.-History:The GMSA was formed on 21...

 under British control to clear the coast of Northern Europe of mines. Several were later also given to France and Norway, and two to Italy.

Eleven of the ships were returned to Germany in 1956/57 and were recommissioned into the Bundesmarine.

Fourteen M1940-type minesweepers (known as the Guadiaro class) were built for the Spanish Navy

Spanish Navy

The Spanish Navy is the maritime branch of the Spanish Armed Forces, one of the oldest active naval forces in the world. The Armada is responsible for notable achievements in world history such as the discovery of Americas, the first world circumnavigation, and the discovery of a maritime path...

in Spanish shipyards. Seven of them were modernised with some help from the US Navy and served in the Spanish Navy for more than thirty years.