QF 4-inch naval gun Mk IV, XII, XXII

The first R class were a class of 62 destroyers built between 1916 and 1917 for the Royal Navy. They were an improvement, specifically in the area of fuel economy, of the earlier Admiralty M-class destroyers. The most important difference was that the Admiralty R class had two shafts and geared turbines, compared with the three shafts and direct turbines of the Admiralty M class, but in appearance the R class could be distinguished from its predecessors by having the after 4-inch gun mounted in a bandstand. The Admiralty ordered the first two of this class of ships in May 1915. Another seventeen were ordered in July 1915, a further eight in December 1915, and a final twenty-three in March 1916.

HMAS Wilcannia was a 1,049-ton anti-submarine and patrol vessel of the Royal Australian Navy (RAN).

The Forward-class cruisers were a pair of scout cruisers built for the Royal Navy in the first decade of the 20th century. The sister ships spent much of the first decade of their careers in reserve. When the First World War began in August 1914 they were given coastal defence missions, Foresight in the English Channel and Forward on the coast of Yorkshire. The latter ship was in Hartlepool when the German bombarded it in December, but never fired a shot. The ships were transferred to the Mediterranean in 1915 and then to the Aegean in mid-1916 where they remained until 1918. They survived the war, but were scrapped shortly afterwards.

The Sentinel-class cruisers were a pair of scout cruisers built for the Royal Navy in the first decade of the 20th century. The sister ships spent about half of the first decade of their careers in reserve and were based in home waters when on active duty. When the First World War began in August 1914 they were given coastal defence missions on the north eastern coast of Britain. The ships were transferred to the Mediterranean in 1915 and then to the Aegean in mid-1916 where they remained until the end of the war in late 1918. Skirmisher was paid off in 1919 and was scrapped the following year, but Sentinel supported the British attempt to intervene in the Russian Civil War for a few months after the end of the war. She also returned home in 1919, but served as a training ship for a few years before she was broken up in 1923.

The Pathfinder-class cruisers were a pair of scout cruisers built for the Royal Navy in the first decade of the 20th century. The sister ships spent much of the first decade of their careers in reserve. When the First World War began in August 1914 they were given coastal defence missions, Pathfinder on the coast of Scotland and Patrol on the coast of Yorkshire. The latter ship was badly damaged when the Germans bombarded Hartlepool in December. She spent the rest of the war in British waters. The ship was paid off in 1919 and sold for scrap the following year. Pathfinder was sunk by a German submarine shortly after the war began, the first sinking of a British warship during the war by a German submarine.

The Adventure-class cruisers were a pair of scout cruisers built for the Royal Navy in the first decade of the 20th century. The sister ships spent about half of the first decade of their careers in reserve and were based in home waters when on active duty. During this time Attentive was involved in two collisions. When the First World War began in August 1914 the ships were given coastal defence missions on the English Channel. Attentive was transferred to Ireland in mid-1915, but Adventure remained with the Dover Patrol for another three years. They were assigned convoy escort duties in the Atlantic Ocean in 1918 before being separated when Attentive was transferred to the Mediterranean and Adventure was tasked to support the British intervention in North Russia. The sisters returned home a few months after the end of the war in November 1918 and were sold for scrap in 1920.

The Acasta class was a class of twenty destroyers built for the Royal Navy under the Naval Programme of 1911 - 1912 that saw service during World War I. They were the last class of Royal Navy destroyers to have mixed names with no systematic theme When the class was designated as "K", names beginning with that letter were allocated to the ships but never used. The class saw extensive wartime service and seven were lost, including four at the Battle of Jutland.

The Laforey class was a class of 22 torpedo boat destroyers of the Royal Navy, twenty of which were built under the Naval Programme of 1912–13 and a further two under the 2nd War Emergency Programme of 1914. As such they were the penultimate pre-war British destroyer design. All served during World War I during which three were lost; the survivors were all scrapped in 1921-23.

The M class, more properly known as the Admiralty M class, were a class of 85 destroyers built for the Royal Navy of United Kingdom that saw service during World War I. All ships were built to an identical – Admiralty – design, hence the class name. 18 other vessels which were officially included within the 'M' class were built to variant designs by three specialist builders – 10 by Yarrow, 6 by Thornycroft, and 2 by Hawthorn Leslie; these are covered in other articles.

The Medea class were a class of destroyers that were being built for the Greek Navy at the outbreak of World War I but were taken over and completed for the Royal Navy for wartime service. All were named after characters from Greek mythology as result of their Greek heritage.

The Faulknor class were a class of flotilla leaders that were under construction in the United Kingdom for the Chilean Navy at the outbreak of World War I. Six ships were ordered by Chile, of which the first two were delivered to Chile before the outbreak of the war. The remaining four ships were purchased by the British, taken over and completed for the Royal Navy for wartime service. In common with Royal Navy convention, they were named after famous Royal Navy captains of the past, in this case the members of the Faulknor family.

The Royal Navy's T class of diesel-electric submarines was designed in the 1930s to replace the O, P, and R classes. Fifty-three members of the class were built just before and during the Second World War, where they played a major role in the Royal Navy's submarine operations. Four boats in service with the Royal Netherlands Navy were known as the Zwaardvisch class.

The British L-class submarine was originally planned under the emergency war programme as an improved version of the British E-class submarine. The scale of change allowed the L class to become a separate class.

The Odin-class submarine was a class of nine submarines developed and built for the Royal Navy (RN) in the 1920s. The prototype, Oberon, was followed by two boats originally ordered for the Royal Australian Navy, but transferred to the RN in 1931 because of the poor economic situation in Australia, and six modified boats ordered for the RN. Three modified boats were built for the Chilean Navy as the Capitan O'Brien-class submarines in 1929.

The Parthian-class submarine or P class was a class of six submarines built for the Royal Navy in the late 1920s. They were designed as long-range patrol submarines for the Far East. These boats were almost identical to the Odin class, the only difference being a different bow shape.

The River class, or Thames class, were a class of submarines built for the Royal Navy. Operating during the Second World War, the three boats of the class comprised Thames, Severn and Clyde. All the submarines were named after rivers in the United Kingdom. One was lost during the war and the rest taken out of service following it.

The S-class submarines of the Royal Navy were originally designed and built during the modernisation of the submarine force in the early 1930s to meet the need for smaller boats to patrol the restricted waters of the North Sea and the Mediterranean Sea, replacing the British H-class submarines. As part of the major naval construction for the Royal Navy during the Second World War, the S class became the single largest group of submarines ever built for the Royal Navy. A total of 62 were constructed over a period of 15 years, with fifty of the "improved" S class being launched between 1940 and 1945.

The Amphion class of British diesel-electric submarines were designed for use in the Pacific War. Only two were completed before the end of hostilities, but following modernisation in the 1950s, they continued to serve in the Royal Navy into the 1970s.

HMS Lance was a Laforey-class destroyer of the Royal Navy. Launched a few months before the outbreak of the First World War and attached to the Harwich Force, Lance took part in several engagements during the war, including the sinking of the Königin Luise and the Battle off Texel. She was responsible for firing the first British shot of the war.

The National Museum of the Royal Navy was created in early 2009 to act as a single non-departmental public body for the museums of the Royal Navy. With venues across the United Kingdom, the museums detail the history of the Royal Navy operating on and under the sea, on land and in the air.

Imperial War Museums (IWM) is a national museum with branches at five locations in England, three of which are in London. Founded as the Imperial War Museum in 1917, the museum was intended to record the civil and military war effort and sacrifice of the United Kingdom and its Empire during the First World War. The museum's remit has since expanded to include all conflicts in which British or Commonwealth forces have been involved since 1914. As of 2012, the museum aims "to provide for, and to encourage, the study and understanding of the history of modern war and 'wartime experience'."

The Heugh Gun Battery is located on the Headland at Hartlepool, County Durham, England. The museum bills itself as the only battlefield of World War I in Great Britain.

Hartlepool is a seaside and port town in County Durham, England. It is governed by a unitary authority borough named after the town which also governs the civil parishes of Greatham, Hart, Dalton Piercy and Elwick. The borough is part of the devolved Tees Valley area. With an estimated population of 90,123, it is the second-largest settlement in County Durham.

County Durham, officially simply Durham, is a ceremonial county in North East England. The ceremonial county was created from the historic County Palatine of Durham in 1853.

The Falkland Islands is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about 300 mi (480 km) east of South America's southern Patagonian coast and about 752 mi (1,210 km) from Cape Dubouzet at the northern tip of the Antarctic Peninsula, at a latitude of about 52°S. The archipelago, with an area of 4,700 sq mi (12,000 km2), comprises East Falkland, West Falkland, and 776 smaller islands. As a British overseas territory, the Falklands have internal self-governance, but the United Kingdom takes responsibility for their defence and foreign affairs. The capital and largest settlement is Stanley on East Falkland.

Sidney is a town located at the northern end of the Saanich Peninsula, on Vancouver Island in the Canadian province of British Columbia. It's 1 of the 13 Greater Victoria municipalities. It has a population of approximately 11,583. Sidney is located just east of Victoria International Airport, and about 6 km (4 mi) south of BC Ferries' Swartz Bay Terminal. The town is also the only Canadian port-of-call in the Washington State Ferries system, with ferries running from Sidney to the San Juan Islands and Anacortes. Sidney is located along Highway 17, which bisects the town from north to south. It is generally considered part of the Victoria metropolitan area.