a recoil-powered short-recoil action, but of a different type, without a toggle.
The standard First World War 3in anti-aircraft gun was Mk I (3in 20 cwt) on a HA Mk II mounting. It was tested in the autumn of 1911 as the future anti-aircraft gun for both army and navy (the navy considered its performance inadequate, but bought it anyway). In Mk II or IIA mountings it armed the following ships: all dreadnoughts except Audacious, all battlecruisers, Lord Nelson class, first five King Edward VIIs, Albion, Prince George, Courageous class, Furious, Vindictive, Minotaur class, Achilles, Cochrane, Duke of Edinburgh, Danae, Dauntless, Dragon, Carlisle, Ceres class, Caledon class, Centaur class, Cleopatra, Conquest, Arethusa class (except Galatea), Chester, Birkenhead and Birmingham, Chatham, Falmouth, and Bristol classes, all scouts (except Pathfinder), Diamond, all large monitors (except Raglan), Gorgon class, M16, M18, M20–M27, minelayers Amphitrite, Ariadne, Latona, carriers Hermes and Campania, balloon ship City of Oxford, and gunboats Cicala, Cockchafer, Cricket and Glowworm. Two guns appear to have been mounted on the submarine E4 in 1916 as an experimental Zeppelin trap. The Mk II gun (not semi-automatic) armed the flotilla leaders Bruce, Campbell, Douglas, Montrose, Scott, Stuart, Shakespeare, Spencer, Wallace, Kempenfelt, Lightfoot and Marksman, and all ‘V&W’ class destroyers, and the submarines J7, K1 to K17, K22 (ex K13), L1 to L4, L7, L15 and M1. In 1940 ‘A’ to ‘I’ class destroyers were ordered rearmed with a single 3in 20 cwt gun on a HA mounting in place of their after sets of torpedo tubes. The 4in gun was rejected because installation entailed too much work and thus too much delay, and magazine stowage presented great difficulties. An ideal position, in place of No 3 gun, was rejected because that gun was so much more effective than No 4 gun on deck. Not all of the planned rearmament was carried out. A few ships later received FKCs and the associated three-man rangefinders. This is the Mk II gun on the Mk III mounting. There was also a disappearing mounting.
A Vickers-built 3in 20 cwt gun, shorn of its sights, at the Finnish National Air Defence museum. (Dr Raymond Cheung)
During the war Italy was given a licence to produce pom-poms, which it designated the Vickers 40/39. Guns were sent to Russia. After the war Japan bought the pom-pom, which was the standard light Japanese light anti-aircraft gun until the mid-1930s, when it was replaced by the French Hotchkiss 25mm.
In 1914 the standard Royal Navy machine gun was the 0.303in Maxim, intended primarily for shore operations and to arm boats.14 These roles largely disappeared after the fall of Belgium, but the guns were now badly wanted for anti-aircraft use on board destroyers and small craft. Guns were surrendered by capital ships so that destroyers could have at least minimal high-angle armament. Until pom-poms became available in mid-1915, many destroyers relied on Maxims and on rifles for air defence. A few heavier Maxims (0.45in calibre) were given high-angle mountings and incendiary bullets.
A Vickers drawing of the 3in 20 cwt HA gun, as the company advertised it after the First World War. The disk with the curves on it is the fuse disk.
The leader Campbell shows her 3in gun amidships, as installed when she was completed. This gun replaced the after bank of torpedo tubes on ‘A’ to ‘I’ class destroyers as modified from 1940 onwards.
The Maxim was the army’s standard weapon, and it was soon evident that it had bought far too few. Thus in September 1914 many navy guns were given to the army in France, and others followed in early 1915 for the expeditionary force attacking the Dardanelles. Remaining guns in the fleet were redistributed so that each destroyer, torpedo boat or small unit operating off the Belgian coast could have a minimum anti-aircraft defence. Capital ships and the earlier light cruisers were left with two guns each. Later light cruisers, all destroyers and certain auxiliaries had one gun each. The War Office began to return Maxims as Vickers guns (in effect, improved light-weight Maxims) became available, but at the same time the Royal Navy was commissioning more and more ships which required machine guns (the official history specially mentions Q ships). Until early 1915 it was impossible to increase the number of Maxims per ship. The navy ordered Vickers guns, but all were diverted to the army because they were more suitable for work ashore; the army gave up all its Maxims in return.
A 12pdr on the HA/LA Mk IX mounting used during the Second World War. This gun was introduced as the main armament of the first British destroyers in 1893. Ammunition was semi-fixed rather than fixed. The standard First World War auxiliary weapon was Mk I or Mk II (the latter introduced for produceability but considered less reliable). Pre-war Mk I production was 1482, plus 1147 in wartime (511 from the United States), and transfers from the army. Mk II: 2010 guns; Mk III was 400 made in Japan. Production resumed for the Second World War, the gun being Mk V. Production amounted to 3494, including 1588 in Canada. Many or all of the Canadian guns were made by the Canadian Pacific Railway Ogden shops in Calgary, hence were called Ogden guns. Both Mks I/II and V were widely used during the Second World War, on board old destroyers, submarines, smaller warships (such as minesweepers, steam Bangor and some Bathurst class, and many large trawlers), auxiliaries and DEMS. The standard Second World War mounting was HA/LA Mk IX. Mk IX was HA Mk VIII modified for gunlayer training; in Mk VIII the gunner elevated the gun by wheel but trained it with his body. Note the characteristic shield; the larger 3in 20 cwt gun was unshielded. During the First World War HA 12pdrs armed the seaplane carriers Nairana and Pegasus and later ‘Hunt’ class minesweepers and boom-defence vessels. This Canadian-made Mk V is in the Alberta Military Museum. (Stephen Magusiak for the Military Museums, Calgary, Alberta)
Versatile shows the 12pdr 12 cwt gun (3in/40) which replaced her after bank of torpedo tubes as part of the emergency destroyer anti-aircraft upgrade program of 1940. In 1940 ‘V&W’ class destroyers were ordered rearmed with this gun (not the 3in 20 cwt) in place of their after torpedo tubes. Surviving old destroyer leaders kept their 3in 20 cwt gun.
Maxim production was suspended in 1917, this gun being superseded by the much lighter air-cooled Lewis gun, introduced into the Royal Navy in 1916. It had first been ordered by the army in 1914, and then used extensively on aircraft, including those of the Royal Naval Air Service. In 1917 Lewis guns were issued in numbers to submarines, minesweepers and patrol ships in the southern part of the North Sea, as they were being attacked at low altitude. They were also issued to defensively armed merchant ships working on the east coast, because they were subject to torpedo and strafing attacks by German seaplanes (there were two torpedo attacks in 1917). Late in 1917 Lewis guns were supplied to cruisers and destroyers off the east coast. By the autumn of 1918 all ships of the Grand Fleet had Lewis guns to deal with low-level attacks. These guns were also supplied to coastal motor boats, motor launches, submarines, and Q-ships. All had been equipped by early 1918. In July 1918 it was decided to arm the main fleet with
