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 Lewis guns to deal with the strafing threat to exposed personnel. The scale of supply was ten per capital ship, eight per cruiser or light cruiser, and four per destroyer. Special naval mountings appeared in the middle of 1918: twins for battleships and cruisers, singles for auxiliary craft. Coastal Motor Boats (CMBs) had both types. Due to shortages, many ships had the American-made Savage-Lewis, which was identical apart from some spare parts. At the end of the war the question of whether the future Royal Navy machine gun should be the Maxim or the Lewis had not been decided (the Lewis was adopted).
Many British First World War auxiliary patrol vessels were armed with Hotchkiss 6pdrs (2.244in or 57mm) in HA mountings.
This 47mm (1.85in)/50 superseded the 3pdr Hotchkiss as a standard light anti-torpedo weapon, and was first mounted in the King Edward VII class. With its higher velocity, it was a better anti-aircraft weapon than the Hotchkiss, and a HA mounting appeared in 1915. For a time these guns were on board the battleship Collingwood, the King Edward VII class pre-dreadnoughts,