HMS ''M21'' was a

First World War World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...

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, West ...

. 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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

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 Dove ...

, she struck a mine off

Ostend Ostend ( nl, Oostende, ; french: link=no, Ostende ; german: link=no, Ostende ; vls, Ostende) is a coastal city and municipality, located in the province of West Flanders in the Flemish Region of Belgium. It comprises the boroughs of Mariakerk ...

in January 1918 and sank off

Dover Dover () is a town and major ferry port in Kent, South East 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 south-east 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 intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regular ...

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

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

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 9.2in 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