View source for M15-class monitor

{{Use British English|date=September 2014}}
{{Use dmy dates|date=April 2020}}
{{more footnotes needed|date=November 2022}}
{|{{Infobox ship begin}}
{{Infobox ship image
|Ship image=HMS M21 WWI IWM SP 2030.jpg
|Ship caption=HMS ''M21''
}}
{{Infobox ship class overview
|Name=''M15'' class
|Builders=
*[[William Gray & Company|William Gray]] (10)
*[[Sir Raylton Dixon]] (4)
|Operators={{navy|United Kingdom}}
|Class before={{sclass|Gorgon|monitor|4|warship}}
|Class after={{sclass|M29|monitor|4|warship}}
|Subclasses=
|Cost=
|Built range=
|In service range= 1915–1959
|In commission range=  
|Total ships building= 
|Total ships planned=
|Total ships completed=14
|Total ships cancelled=
|Total ships active=
|Total ships laid up=
|Total ships lost=3
|Total ships retired=
|Total ships preserved=
}}
{{Infobox ship characteristics
|Hide header=
|Header caption= 
|Ship type=[[monitor (warship)|Monitor]]
|Ship displacement=540 tons
|Ship length={{convert|177|ft|3|in|m|abbr=on}} 
|Ship beam={{convert|31|ft|m|abbr=on}} 
|Ship height=
|Ship draught={{convert|6|ft|9|in|m|abbr=on}} 
|Ship power=
|Ship propulsion=*2 shafts
*Triple-expansion
* {{convert|800|hp|abbr=on}}
*4 shaft
*Bolinder 4-cylinder semi-diesel
* {{convert|640|hp|abbr=on}}
*4 shafts
*Campbell 4-cylinder paraffin engines
* {{convert|560|bhp|abbr=on}}
|Ship speed={{convert|11|kn|lk=in}}
|Ship range=
|Ship endurance=
|Ship complement=69
|Ship sensors=
|Ship EW=
|Ship armament=
*1 × [[BL 9.2 inch gun Mk IX–X|BL {{convert|9.2|in|adj=on|sigfig=4}} Mk X gun]] (''M15''-''M18'') or [[BL 9.2 inch gun Mk I–VII|BL 9.2-inch Mk VI gun]]
*1 × [[QF 12-pounder 12 cwt naval gun|12-pdr (76mm) QF Mk 1 gun]]
*1 v [[QF 6-pounder Hotchkiss|6-pdr (57mm) QF MK 1]] AA gun
|Ship armour=
|Ship armor=
|Ship notes=
}}
|}

The '''''M15'' class''' comprised fourteen [[monitor (ship)|monitor]]s of the [[Royal Navy]], all built and launched during 1915.

== Design ==
The ships of this class were ordered in March, 1915, as part of the [[Emergency War Programme]] of ship construction. They were designed to use the [[BL 9.2 inch gun Mk I–VII|9.2 inch Mk VI gun]] turrets removed from the {{sclass|Edgar|cruiser|4}} and the [[BL 9.2 inch gun Mk IX–X|Mk X]] turrets held in stock for the {{sclass|Drake|cruiser|0}} and {{sclass|Cressy|cruiser}}s.  This resulted in the first four of the class, which were built by [[William Gray & Company]] of [[Hartlepool]], receiving the Mk X mounting.  The remaining ten ships, all built by [[Sir Raylton Dixon & Co.]], [[Middlesbrough]], all received the Mk VI mounting.

During September 1915, the 9.2&nbsp;inch guns of HMS ''M24'', ''M25'', ''M26'' and ''M27'' were removed for use as artillery.  These were replaced by [[BL 7.5-inch Mk II – V naval gun|7.5-inch guns]]. ''M24'' and ''M25'' received the spare guns reserved for the recently sunk [[pre-dreadnought]] [[battleship]] {{HMS|Triumph|1903|2}}, ''M26'' received one of ''Swiftsure''{{'}}s spare guns. ''M27'' received 6-inch (M27) guns.

''M21'' and ''M23'' also had their 9.2-inch gun removed in 1917, receiving 7.5-inch guns from the decommissioned pre-dreadnought {{HMS|Swiftsure|1903|2}}.

The class used a mixture of propulsion methods.  ''M21'' and '' M22'' were fitted with conventional triple-expansion steam engines, ''M24'' was fitted with four-cylinder paraffin engines, and the remainder received Bolinder four-cylinder semi-diesel engines.

Admiral [[Reginald Bacon]], who had commanded several of the M15 class in the [[Dover Patrol]], wrote about his experiences with the ships of the patrol in 1919. While generally positive about the performance of the design, he noted that they had a tendency to [[Ship motions#Rotational motions|roll]], using a specific occasion with ''M25'' as an example;
:"The ''M25'', while in the mouth of the Thames at anchor, rolled 180 degrees in ten seconds - that is, she made two complete rolls of 45 degrees each way, each occupying only five seconds."{{sfn|Bacon|1919|loc=vol 1, p. 67}}

== Service ==
''M25'', ''M26'', ''M27'' and ''M28'' served in the Dover Patrol from 1915 to 1918.  The remainder served [[Naval warfare in the Mediterranean during World War I|in the Mediterranean]] from 1915, with ''M23'' joining the Dover Patrol in June 1917 and ''M21'' in October 1917.

As part of the [[North Russia Intervention|intervention into the Russian civil war]] ''M23'', ''M24'', ''M25'' and ''M27'' served in support of British and [[White movement|White Russian]] forces in the [[White Sea]] in May to September 1919.

''M22'' was converted to a [[minelayer]] in 1920, whilst ''M23'' became a [[training ship|drill ship]], surviving until 1959.

== Ships of the class ==

*''[[HMS M15|M15]]'' - launched on 28 April 1915 and sunk by {{SMU|UC-38||2}} on 11 November 1917.
*''[[HMS M16|M16]]'' - launched on 3 May 1915 and sold 29 January 1920.
*''[[HMS M17|M17]]'' - launched on 12 May 1915 and sold 12 May 1920.
*''[[HMS M18|M18]]'' - launched on 15 May 1915 and sold 29 January 1920.
*''[[HMS M19|M19]]'' - launched on 4 May 1915 and sold 12 May 1920.
*''[[HMS M20|M20]]'' - launched on 11 May 1915 and sold 29 January 1920.
*''[[HMS M21|M21]]'' - launched on 27 May 1915 and mined 20 October 1918.
*''[[HMS M22|M22]]'' - launched on 10 June 1915, renamed ''Medea'' 1925 and sold December 1938
*''[[HMS M23|M23]]'' - launched on 17 June 1915, renamed ''Claverhouse'' 1922 and sold 1959
*''[[HMS M24|M24]]'' - launched on 9 August 1915 and sold 29 January 1920.
*''[[HMS M25|M25]]'' - launched on 24 July 1915 and scuttled 16 September 1919
*''[[HMS M26|M26]]'' - launched on 24 August 1915 and sold 29 January 1920.
*''[[HMS M27|M27]]'' - launched on 8 September 1915 and scuttled 16 September 1919
*''[[HMS M28|M28]]'' - launched on 28 June 1915 and sunk during the [[Battle of Imbros]] 20 January 1918

==References==
{{reflist}}

==Bibliography==
* {{cite book <!-- {{sfn|Bacon |1919|loc=vol. x, p. x}} -->  |last=Bacon |first=Reginald |author-link=Reginald Bacon |title=The Dover Patrol 1915-1917 |year=1919 |others=(2 vols.) |publisher=George H. Doran Co. |location=New York}}&nbsp;[https://archive.org/stream/doverpatrol01bacogoog#page/n6/mode/2up Vol. 1] • [https://archive.org/stream/doverpatrol00bacogoog#page/n10/mode/2up Vol. 2]
*{{cite book |last1=Buxton |first1=Ian |title=Big Gun Monitors: Design, Construction and Operations 1914–1945 |location=Barnsley, UK |publisher=Seaforth Publishing |year=2008 |orig-year=1978 |edition=2nd Revised |isbn=978-1-84415-719-8 }}
*{{cite book |last1=Crossley |first1=Jim |title=Monitors of the Royal Navy; How the Fleet Brought the Great Guns to Bear |location=Barnsley, UK |publisher=Pen & Sword |year=2013 |isbn=978-1-78383-004-6 }}
*Dittmar, F. J. & Colledge, J. J., "British Warships 1914-1919", (Ian Allan, London, 1972), {{ISBN|0-7110-0380-7}}
*{{cite book |last1=Dunn |first1=Steve R |title=Securing the Narrow Sea: The Dover Patrol 1914–1918 |location=Barnsley, UK |publisher=Seaforth Publishing |year=2017 |isbn=978-1-84832-251-6 }}
* {{cite book|last=Friedman|first=Norman|title=Naval Weapons of World War One: Guns, Torpedoes, Mines and ASW Weapons of All Nations; An Illustrated Directory|publisher= Seaforth Publishing|location=Barnsley|year=2011|isbn=978-1-84832-100-7 |author-link=Norman Friedman}}
*Gray, Randal (ed), "Conway's All the World's Fighting Ships 1906–1921", (Conway Maritime Press, London, 1985), {{ISBN|0-85177-245-5}}
*{{cite book |year=1969 |orig-year=First published 1919 |editor1-last=Parkes |editor1-first=Oscar |editor2-last=Prendergast |editor2-first=Maurice |title=Jane's Fighting Ships 1919 |journal=Fighting Ships |url=https://catalog.hathitrust.org/Record/012202881 |location=New York |publisher=Arco Publishing Co |isbn=978-0-71534-716-4 |oclc=1902851 |access-date=23 December 2019 }}

==External links==
{{Commons category|M15 class monitor}}

{{M15 class monitors}}
{{WWI British ships}}

{{DEFAULTSORT:M15 Class Monitor}}
[[Category:Monitor classes]]
[[Category:M15-class monitors| ]]