HMS ''M21'' was a

First World War World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

monitor Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, Wes ...

. After service in the

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

and the

Dover Patrol The Dover Patrol and later known as the Dover Patrol Force was a Royal Navy command of the First World War, notable for its involvement in the Zeebrugge Raid on 22 April 1918. The Dover Patrol formed a discrete unit of the Royal Navy based at Dov ...

, she struck a mine off

Ostend Ostend ( ; ; ; ) is a coastal city and municipality in the province of West Flanders in the Flemish Region of Belgium. It comprises the boroughs of Mariakerke, Raversijde, Stene and Zandvoorde, and the city of Ostend proper – the la ...

in January 1918 and sank off

Dover Dover ( ) is a town and major ferry port in Kent, southeast England. It faces France across the Strait of Dover, the narrowest part of the English Channel at from Cap Gris Nez in France. It lies southeast of Canterbury and east of Maidstone. ...

Design

Intended as a shore bombardment vessel, ''M21''s primary armament was a single 9.2 inch Mk VI gun removed from the HMS ''Theseus''. In addition to her 9.2 inch gun, she also possessed one 12 pounder and one six pound anti-aircraft gun. Due to the shortage of Bolinder diesel engines that equipped her sisters, she was fitted with 2 shaft triple expansion steam engines that allowed a top speed of eleven knots. The monitor's crew consisted of sixty nine officers and men.

Construction

HMS ''M21'' ordered in March, 1915, as part of the

War Emergency Programme War is an armed conflict between the armed forces of State (polity), states, or between governmental forces and armed groups that are organized under a certain command structure and have the capacity to sustain military operations, or betwe ...

of ship construction. She was laid down at the Sir Raylton Dixon & Co. Ltd shipyard at

Govan Govan ( ; Cumbric: ''Gwovan''; Scots language, Scots: ''Gouan''; Scottish Gaelic: ''Baile a' Ghobhainn'') is a district, parish, and former burgh now part of southwest Glasgow, Scotland. It is situated west of Glasgow city centre, on the sout ...

in March 1915, launched on 27 May 1915, and completed in July 1915.

World War I

''M21'' served initially in the

from September 1915. On her return from the Mediterranean in September 1917, ''M21'' had her main 9.2 in gun removed, as it was required for artillery use on the Western Front, and a BL Mk III 50-caliber gun was fitted in lieu. ''M21'' then served with the

from October 1917.

Loss

''M21'' struck a mine off Ostend on 20 October 1918. She was taken in tow to Dover, but sank off West Pier.

Citations

References

* *Dittmar, F. J. & Colledge, J. J., "British Warships 1914-1919", (Ian Allan, London, 1972), {{DEFAULTSORT:M21 M15-class monitors 1915 ships World War I monitors of the United Kingdom Ships sunk by mines Maritime incidents in 1918 World War I shipwrecks in the English Channel Royal Navy ship names