The BL 9.2-inch Mk IX and Mk X gunsMk IX = Mark 9, Mk X = Mark 10. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence these were the ninth and tenth models of BL 9.2-inch gun. were British breech loading guns of 46.7 calibre, in service from 1899 to the 1950s as naval and coast defence guns. They had possibly the longest, most varied and successful service history of any British heavy ordnance.

History The Mk IX/X guns succeeded the BL 9.2-inch Mk VIII naval gun and increased the bore length from 40 to 46.7 calibres, increasing the muzzle velocity from .

The Mk IX was designed as a coast defence gun, with a three-motion breech. Only fourteen were built and the Mk X, introduced in 1900 and incorporating a single-motion breech and changed rifling, succeeded them. As coastal artillery, the Mk X remained in service in Britain until 1956, and in Portugal until 1998. A total of 284 of the Mark X version were built by Vickers, of which 25 examples are known to survive today, all except one fitted on barbette mounts. The exception is a gun in Cape Town, South Africa on a disappearing mount. Another four guns manufactured by Elswick Ordnance Company survive, mounted in turrets.

The 9.2-inch Mk XI gun introduced in 1908 increased the bore length to 50 calibres in an attempt to increase the velocity still further, but proved unsuccessful in service and was phased out by 1920. The Mk X was hence the final Mark of 9.2-inch guns in widespread British Commonwealth service.

The BL 9.2 also affected the development of radar. Immediately before the Second World War, an army team developed a surface-scanning radar to detect enemy ships in the English Channel. By chance, in July 1939 one of these radars was being tested while the 9.2-inch battery at Brackenbury Battery outside Harwich was firing. The radar team noticed odd returns on their displays, and realised that these were due to the waterspouts caused by the shells exploding in the water creating a vertical surface off which the signals reflected. The use of radar to accurately spot the fall of shells was rapidly developed, and was widespread by the war's end.

Design

These were medium-velocity wire-wound guns with Welin interrupted screw breeches.

Naval service Royal Navy

Mark X guns were mounted on : Cressy-class armoured cruisers commissioned from 1901 Drake-class armoured cruisers commissioned from 1902 Duke of Edinburgh-class armoured cruisers commissioned from 1906 Warrior-class armoured cruisers commissioned from 1907 King Edward VII-class battleships commissioned from 1905 M15-class monitors M15, M16, M17, M18 from 1915

Greek Navy

Four guns of 45 calibres () bore produced by Elswick Ordnance CompanyDiGiulian were mounted in two twin turrets on the Greek cruiser Georgios Averof in 1910, instead of the guns mounted on her sisters of the Pisa-class in Italian service. These were similar to the four Vickers 45-calibre export model guns used by Britain as railway artillery on the Western Front in World War I under the designation BL 9.2-inch gun Mark XIV. They fired the same shell using the same cordite charge as the British service Mk X gun, and it may be assumed that its performance was very similar.

British coastal deployments

These were 'counter-bombardment' guns designed to defeat ships up to heavy cruisers armed with guns. They were deployed in the fixed defences of major defended ports throughout the British Empire until the 1950s.

Their role was to defeat enemy ships attacking the ships in a port, including warships, alongside or at anchor in the port. However, where guns covered narrows, such as the Dover Straits, the Straits of Gibraltar, or the Narrows of Bermuda, they also had a wider role of engaging enemy ships passing through the straits. Normally deployed in batteries of two or three guns, a few major ports had several batteries positioned miles apart.

There were several marks of mountings and a battery had extensive underground facilities in addition to the guns visible in their individual gun-pits. Together with the Mk VII, they provided the main heavy gun defence of the United Kingdom in World War I. Three Mk IX and 53 Mk X guns were in place as of April 1918.Farndale 1988, page 404

Mounting The Mounting Barbette Mark V (the original mounting with Mark IX and X guns) gave a maximum elevation of 15 degrees, and maximum range of . This and some modified to Mark VI (30 degrees and ) were manually powered, the projectile and propelling charge were manually hoisted to loading level, the projectile manually loaded and rammed, and traverse and elevation were by handwheels. There was an elevated platform around the breech area for the gun detachment commander (No 1) and some detachment members, and a Gun shield to the front. The ordnance and mounting together weighed some 125 tons, they were well balanced and the handwheels needed very little effort to move the gun.Hogg 1998 pg 168

However, the Mark VII mounting appeared in the 1930s and in 1939 a simplified version, Mark IX. Both were hydraulically powered and the platform was enclosed in a roofed gun house with three sides (and rear with Mark IX). The hydraulics meant that both projectile and propelling charge could be hoisted in a single load. With Mark VII and IX the maximum elevation was increased to 35 degrees to give a maximum range of .

Installation

Each gun mounting was installed on a central cast-steel pedestal in an open concrete gunpit in diameter and deep. The gun and mounting weighed 125 tons. A very narrow gauge rail track was embedded around the gunpit floor. A trolley was manhandled around the track between the two ammunition lifts (one for projectiles, one for propelling charges) and the rear of the gun (this position varied depending on where the gun was pointed).

Below the gun pit were the separate ammunition bunkers for projectiles and shells with direct access to the ammunition lifts. These bunkers had an access road leading to them for ammunition re-supply. The guns presented only a very small target above ground level, guns and gunpits were camouflaged.

Organisation Two or three guns comprised a named battery position with the guns manned by a Heavy Battery. For example, in 1940 Madalena and Bijemma batteries, both with 9.2 in Malta were manned by 6 Heavy Battery RA of 4 Heavy Regiment RA.Maurice-Jones 1957 pg 256

Increasing ranges led to new centralised control arrangements. Fortress observation posts, equipped with rangefinders and directors were sited apart to give observation of all the sea area within range. They reported enemy ship bearings and distances to the 'fortress plotting centre' (FPC) where the attackers' positions and courses were plotted, converted to coordinates and then assigned as targets to batteries by the fire commander. The details were telephoned to batteries. The battery plotting room used a coordinate converter to turn the coordinates into bearings and elevations and transmitted them to the guns where pointers were matched by changing the guns’ traverse and elevations.Maurice-Jones 1957 pg 215

The observers also reported fall of shot relative to the targets, the FPC used an encoder to convert these into a clock code, which the battery converted to its left/right, add/drop corrections. Various types of radars integrated into the fire command soon became widespread in WW2 and enabled effective night engagements.

Deployments The following table summarises the deployment of 9.2-inch guns.Maurice-Jones, 1957, pgs 219–224, 229, 246, 251, 256Nicholson, 1972, pgs 448, 453, 468, 480Horner, 1995, pg 204Northling, 1987, pg 343-348 It is possible that some 1914 guns were still the older marks. * indicates deployment was not completed until after 1940. A third Canadian battery was not completed until after World War II. The three guns in the Imperial fortress colony of Bermuda remained in battery through the Second World War (and are still in situ), but were not actively utilised. More were requested by the Governor and military General Officer Commanding (GOC), Lieutenant-General Sir Denis Kirwan Bernard, to be sent to the Bermuda Garrison during the war, but the build-up of United States Army Coast Artillery Corps batteries in Bermuda from 1941 as part of the United States armed forces' Bermuda Base Command rendered this unnecessary.

+ Ports defended by 9.2-inch guns Port Country/territory World War I World War II Dover United Kingdom 5 6 Medway & Thames United Kingdom 4 2 Harwich United Kingdom 0 2 Tyne United Kingdom 2 1 Tees & Hartlepool United Kingdom 0 1 Humber United Kingdom 0 2 Solent United Kingdom 14 6 Portland United Kingdom 6 4 Plymouth United Kingdom 8 6 Milford Haven United Kingdom 4 2 Forth United Kingdom 6 3 Cromarty United Kingdom 3 0 Lough Swilly Ireland 2 0 Queenstown Ireland 4 0 Berehaven Ireland 2 0 Gibraltar Gibraltar 14 8 Freetown Sierra Leone 2 2 St. George's Bermuda 3 0 Kingston Jamaica 1 0 Valletta Malta 16 7 Cape Town South Africa 2 7 Simonstown South Africa 3 3 Durban South Africa 0 3* Port Louis Mauritius 2 Colombo Sri Lanka 4 2 Trincomalee Sri Lanka 0 2 Singapore Singapore 5 6 Hong Kong Hong Kong 0 8 Sydney – North Head Australia 0 2 Sydney – Cape Banks Australia 0 2 Port Kembla – Drummond Battery Australia 0 2 Newcastle - Fort Wallace Australia 0 2 Fremantle – Rottnest Island Australia 0 2 Fremantle – Garden Island Australia 0 2* Darwin – East Battery Australia 0 2 Halifax Canada 0 3* Vancouver Island Canada 0 2* Auckland – Stony Batter New Zealand 0 2* Auckland – Whangaparaoa New Zealand 0 2* Wellington – Wrights Hill Fortress New Zealand 0 2*

Portugal has several surviving examples, with live firings as recently as 10 December 1998. The Portuguese refer to these guns as 23.4 cm guns, made by Vickers.

Deployment on railway trucks

In 1916 Elswick adapted a small number of Mk X guns, 2 Mk X variants originally intended for coast defence in Australia, and 4 45-calibre Vickers export guns (under the designation 9.2-inch gun Mk XIV) and mounted them on Mk 3 railway truck mountings for service on the Western Front in France and Belgium.Hogg & thurston 1972, page 168-169

Belgian coast From 1917 several Mk X guns were deployed ashore on the section of the Belgian coast still held by the Allies, near Nieuport. They were part of the "Royal Naval siege guns" under the command of Admiral Sir Reginald Bacon, and were used for attacking German heavy gun batteries.

Other deployments In the 1950s, Canadian guns were transferred under NATO auspices, to Portugal (Azores) and Turkey. It is unclear if any UK guns were also transferred.

Surviving examples

Of the original ninety-eight 9.2-inch guns that did service worldwide during WWII, only twenty-nine remain. Of these twenty-nine, thirteen are in South Africa, the De Waal Battery No. 3 gun being the only gun in the world that has been restored as a moving display.

Australia two 9.2-inch guns in the Oliver Hill Battery on Rottnest Island, off Fremantle, Western Australia. One, known as the H1 Gun, is restored; its companion H2 Gun is awaiting restoration

Bermuda two Mk X guns on St. David's Island, on Mark V Barbette mounts, at St. David's Battery, overlooking the Narrows Channel that leads to St. George's Harbour, in Bermuda, as well as to the Royal Naval Dockyard, Bermuda, the Great Sound, Hamilton Harbour, and Murray's Anchorage. The battery forms part of Great Head Park, and there is public access. one Mk X gun, previously at Fort Victoria on St. George's Island, since relocated to the Bermuda Maritime Museum at the Royal Naval Dockyard to make way for a hotel development, and was emplaced (though not on its mount) for display in the Keep of the fortified dockyard in 2021, after eleven years of storage.

Gibraltar three 9.2-inch guns, one each at O'Hara's Battery, Lord Airey's Battery and Breakneck Battery

Greece