Cabinet formed an Equipment Committee which in 1902 finally settled on a Vickers design for the carriage's recoil system, an Armstrong design for the gun and the National Ordnance Works's design for the sighting and elevation gear and ammunition system. Together with a modern long recoil system, for the first time a gunshield was incorporated, dial sights were added, sights did not have to be removed before firing as previously, wheel size was reduced from to which saved weight and had been demonstrated to be effective on the Ehrhardt gun.
The 18 pounder was introduced along with the smaller but otherwise similar 13-pounder in 1904, the 18-pounder was found in use on all fronts during World War I. Put into reserve during the inter-war era, some were converted into the famed 25 Pounder design, while many others were re-activated for training or coastal defence.
The development of Marks of the gun and carriage occurred on different timescales and hence the Marks of gun and carriage need to be differentiated.
The Mk I gun had a wire-wound barrel, chosen as it was lighter, stronger and cheaper to manufacture than a built-up barrel. The Mk I gun and Mk I carriage were accepted into service on June 30 1904. The narrow single pole trail design of the Carriages Mk I and II was suited to towing by teams of horses but limited the gun's range to 6525 yards in normal use as it restricted downward motion of the breech and hence muzzle elevation. The range could be increased to 7800 yards by "digging in" the end of the pole trail to increase elevation. Its distinguishing feature was the barrel, significantly longer than the 13 pdr's and significantly longer than the recuperator housing above it.
The early versions of 18 pounder anti-aircraft guns remained in service, apparently only in the home defense of Britain. 35 were in service in Britain in June 1916 and 56 at the end of World War I. After the war they were converted back to field gun use by removing the cartridge retaining catch.
Battlefield experience in 1914 and 1915 showed up the weakness of the original recuperator springs (which returned the barrel to firing position after recoil) and loss of oil in the recuperator under intense firing. Poor quality of wartime manufacture of the springs was also a factor. Spring shortages due to breakages meant guns remained in the firing line and had to be "run up" - have the barrel moved forward into its firing position - by hand, hence slowing the rate of fire. A temporary preventive measure was the addition of a distinctive armoured box-shaped oil reservoir to the front end of the recuperator to maintain the oil supply and extend spring life. This modification is visible in many photographs of 18 pdrs in action on the Western Front right up to the end of World War I.
The recuperator spring problem was rectified with the new Mk II carriage officially introduced in the field in November 1916 with a hydro-pneumatic recuperator design which replaced the recuperator springs and could be fitted into the existing spring housing by battery officers in the field. It is identified by the torpedo-shaped extension on the recuperator, which made the recuperator assembly nearly as long as the barrel and hence altered the equipment profile. Converted existing carriages were designated Mk I*. The Mk II carriage also incorporated a longer cradle.
The major variant was the Mark IV gun, which started testing in 1916. It eliminated the original central pole trail which had restricted elevation and introduced a box trail (initially carriage Mk III, later Mk. IV) which allowed increased elevation and hence increased maximum range from 6525 to 9300 yards. The recoil system was updated with a new variable-recoil hydropneumatic system and moved from above to below the gun barrel. The new single-motion "Asbury breech" allowed for higher rates of fire. A single battery of the Mk IV gun on the early Mk III carriage was serving with 4th Army when World War I ended. The new gun and carriage was in effect a new weapon but as the calibre and ammunition remained the same it was referred to as part of the 18 pdr development cycle until the calibre was phased out.
By 1919 the standard British field gun was the 18 pounder Mk IV gun on Mk IV carriage but Britain still possessed many of the older Marks.
In the early 1930s many of the surviving Mk. IV's were converted into 25-pounders by re-boring to take an 87.6mm liner (25-pounder calibre), while earlier weapons were not bothered with.
The Mk V carriage with split trail was introduced in the 1930s, allowing wider traverse, and existing marks updated with modern pneumatic tyres for towing by motor vehicles.
Throughout World War I, the 18 pounder was operated by the Royal Field Artillery as the standard field gun. Royal Horse Artillery batteries were also re-equipped with it as their 13 pounders proved unsuited to the prevalent trench warfare.
The gun and its 2-wheeled ammunition limber were towed by a team of 6 vanner (light draught) horses in pairs - lead pair, centre pair, limber pair. A driver rode the left horse of each pair. The ammunition limber was hooked up to the horses and the trail of the gun was hooked up to the limber, so the total weight of the gun and trail were supported on 4 wheels. The 4-wheeled ammunition wagon was towed separately. The gun crew all rode into action either on their own horses or on the limber and wagons. In early actions of the war the ammunition limber was positioned on the left of the gun, and ammunition was passed from there to the loader, but as the war progressed and larger quantities of ammunition were fired ammunition was dumped in quantity at prepared positions next to gun pits.
Initially, British Regular Army and Dominion (e.g. Australia, New Zealand, Canada) infantry divisions were equipped with 3 field artillery brigades each with 3 batteries of 6 18 pounders (total 54 per division), and a brigade of 4.5 inch howitzers. New Army and Territorial Force division batteries had 4 guns (total 36 per division). From February 1917, all divisions were standardised with 2 artillery brigades each with 3 batteries (named A, B and C) of 6 18 pounders (total 36 per division) and 1 battery (D) of 6 4.5 inch howitzers (total 12 per division). The remaining 18 guns from Regular divisions were transferred to Army control in Army Field Artillery Brigades, to be available for more flexible deployment.
When World War I began, British field guns (13 pounder and 18 pounder) were equipped solely with shrapnel shells, with an approximate 3-1 ratio of field guns to field howitzers (5 inch and 4.5 inch). The 18 pounder shrapnel shell contained 374 small balls with a timer fuse set to blast them forward out of the front of the shell just above and in front of the target, much like a large shotgun blast. Hence at a theoretical maximum 20 rounds per minute it could deliver 7,480 lethal projectiles per minute at a far greater range than machine-guns could attain at the time. The gunners and officers of Regular Army field artillery batteries were expert at closely supporting the "fire and movement" tactics of the infantry with accurate low-bursting shrapnel fire. Shrapnel was successful in the early defensive battles in Belgium and France, against German troops attacking in the open. As the war of movement ended and static trench warfare became the norm with Germany in a defensive position on the Western Front, shrapnel had little effect on enemy troops protected by trenches and was to some extent replaced by the machine-gun in open warfare. The first trial high-explosive TNT rounds were fired in action on 31 October by 70th Battery, 34th Brigade RFA and 54th Battery, 39th Brigade RFA on the Ypres front and were quite successful, demonstrating both that they could destroy enemy guns and kill troops. From then on Britain increasingly supplied 18 pounders with HE (high explosive) shells.
A major lesson learned in 1914 was that the early British doctrine of positioning field guns in open or semi-open positions made them vulnerable to enemy artillery fire, and subsequently more use would be made of available sheltered and hidden positions for firing. This made the role of the Forward Observation Officer (FOO) crucial for 18 pounder batteries providing fire support for advanced infantry as they could no longer rely on direct line of sight. These officers suffered high casualties. It is instructive to compare the photograph of the 18 pounder gun in the open at the 1914 Battle of the Marne with that below of the gun almost hidden in a pit at the Second Battle of Bullecourt in 1917.
With Britain now attacking on the Western Front from 1915 onwards, 18 pounders fired shrapnel shells to cut enemy barbed-wire defenses, and high explosive shells to attack troops in trenches. From 1916 light and medium mortars were increasingly used to blow aside barbed wire defenses.
The 18 pounder continued to be used as a general-purpose light gun in other theatres, such as on Gallipoli where it was manhandled up onto mountain ridges because of the lack of a modern mountain gun. The 18 pounder could attack lightly protected troops by destroying the parapets of trenches, small houses, barricades. But its relatively flat high velocity trajectory meant that it could not reach an enemy sheltering out of the direct line of sight, in dips in the ground, on reverse slopes (such as the Quadrilateral east of Ginchy on the Somme) or in deep trenches or cellars. It lacked the power to demolish fortifications, and it became apparent that Britain's doctrine of reliance on light guns was unsuited to modern mechanised warfare - German artillery had a 2-1 ratio between field and heavy artillery, with many mortars, whereas Britain's was 20-1 in mid-1915 with few mortars. British planners realised they would need a 2-1 ratio for a successful offensive while the French believed they needed 1-1. General Farndale justifies the retention of 2-1 field artillery as "Field guns were essential to attack targets close to our own troops and to play their part in the tactical plan".
The January 1917 "Artillery in Offensive Operations" estimated 18 pounders needed 7.5 shrapnel rounds + 5% HE per yard of front at medium range to cut barbed wire defences, and 20 rounds of HE to destroy trenches in enfilade. Destruction of trenches frontally was generally estimated as requiring twice the enfilade amount. It was estimated that an 18 pounder would fire 200 rounds per day in an "all out" offensive. It expressed a preference for shrapnel with a long corrector in creeping barrages due to its high number of "man-killing missiles" [374 balls] and its smoke cloud (shrapnel shells were designed to produce a white puff of smoke on bursting, originally as an aid to gunnery spotting). HE was viewed as not providing this necessary visual screen but could be considered for use in creeping and back-barrages in conjunction with smoke shell, but smoke shell was considered "still in its infancy".
In its February 1917 Technical Notes on 18 pounder Barrages, GHQ stated shrapnel and HE barrages would normally cover to a depth of 200 yards and expressed its preference for timed shrapnel (T.S.) for creeping barrages, due partly to shrapnel directing its force forward hence being safer for those following especially if it fell short. 50% air bursts and 50% percussion (bursting on contact) was considered optimal except on "very bad ground" where percussion rounds would mostly be wasted. HE with its lateral bursting was considered more dangerous to advancing troops (as they were assumed to be in a line abreast) than shrapnel if it burst short, but lateral bursts were considered to have less effect on the enemy as they had less "forward effect". HE with delay was difficult for advancing troops to stay close behind as it burst 30-40 yards beyond the point of initial contact. HE without delay was assessed as effective only if it burst actually in the enemy trench. With a proper barrage program and fuze setting, timed shrapnel creeping barrage was considered optimal. British regular army field gunners were already proficient in accurately timed low shrapnel bursts in 1914, as demonstrated in the early battles, but few remained by early 1917 and many gunners were relatively new recruits and inexperienced; HE had only been in use with 18 pounders for 2 years, so this note perhaps reflects a desire to stick with a proven method for which they could still draw on a nucleus of experts. Shrapnel appears to have been favoured for creeping barrages and a mix of shrapnel and HE for standing barrages and other tasks.
The British advance in pursuit of the German army in early 1917 as it withdrew to stronger positions on the Hindenburg Line brought a brief resumption of mobile warfare, and from the experience GHQ emphasised the need to get all light weaponry as far forward as possible to support infantry, and that "Covering fire of 18-pounders and howitzers can not be too far exploited" [i.e. should be exploited as much as possible]. It also warned : "There was tendency, due to trench warfare, among C.R.A.s to attempt to control individual batteries. Brigade or group commanders should be given a task and allowed to carry it out".
At the opening of the Battle of Arras on April 9 1917 the order was for 18 pounders to fire 50% HE and 50% shrapnel shells in the creeping barrage ahead of the advancing infantry, with 1 gun for every 20 yards of front. While a few commanders varied this slightly, such as Brigadier-General Tudor, CRA of 9th Division, who chose 75% HE and 25% smoke, the opening was notable for the first use of a coordinated fireplan across the whole front of several Armies, with a common strategy linking infantry with artillery and coordinating the advance of various types of artillery. For instance the 18 pounders were to move forward when the infantry reached their phase 2 objective and the 60 pounders and howitzers would move forward to take their vacated firing positions. This contrasted with the Somme where individual Corps and Division commanders used their own fire plans and assault tactics.
For the Third Battle of Ypres in July 1917 the plan was for wire cutting to be done by mortars and howitzers, "to conceal the strength of the field guns". 1,098 18 pounders, 1 every 15 yards on average, would include shrapnel in firing a creeping barrage starting close to the British trenches and moving forward at 100 yards in 4 minutes. Field batteries were to advance beyond no-mansland as the priority was to protect the infantry while they were "consolidating on their objectives" (i.e. gaining and holding new advanced positions).
In the opening barrage for the first phase on 31 July, the Battle of Pilckem Ridge, 2/3 of the 18 pounders fired in the creeping barrage at 4 rounds per minute and 1/3 fired in the standing barrage on the German second line.. The barrage was generally successful but as the weather deteriorated and tracks turned to mud and shellholes filled with water it became nearly impossible for guns to advance in support of the infantry as planned.
For the opening barrage at the Battle of Menin Road on 20 September the ratio of medium/heavy artillery to field artillery reached 1 - 1.5 for the first time, reflecting more heavy guns rather than fewer field guns. 18 pounders were to fire 50%-50% shrapnel and HE with 25 % of the HE fuzes set to delay. Hence the previous doubts about HE appear to have been overcome, and for the lifting barrage for the Battle of Cambrai on 20 November (this was chosen rather than a creeping barrage) the 18 pounders were to fire equal proportions of shrapnel, HE and smoke, with the precise smoke usage depending on weather conditions at the time.
A total of 47,992,000 18 pounder rounds were manufactured in 1917 and 38,068,000 were fired (38% of its total for the whole war) indicating the extent to which the artillery war escalated in 1917.
For the successful British attack at the Battle of Amiens on 4 July there was one 18 pounder per 25 yards of front, supplemented by machine-guns, and they fired a barrage of 60% shrapnel, 30% HE and 10% smoke 200 yards ahead of the advancing troops. By the end of World War I the modern "empty battlefield" was evolving, with troops learning to avoid open spaces, and the light field gun was becoming obsolete. Increasing use of light machine-guns, light mortars and field howitzers with their high trajectory were able to drop shells onto even deeply sheltered enemy troops on reverse slopes which field guns could not reach. The 18 pounder Mk IV, with its box trail which allowed it to fire in a high trajectory, began its evolution into the more versatile 25 pounder gun-howitzer.
At the Armistice there were 3,162 18 pounders in service on the Western Front and it had fired approximately 99,397,670 rounds.
The gun remained in service until the 1950s and 60s when it was replaced by the 25 pounder. Some examples remain preserved, including several in Collins Barracks, Cork.
(carriage Mk IV box trail & Mk V split trail)
This shell does not have the red band around the neck, indicating it has not been filled
The red band indicates it has been filled. The green band indicates it is filled with amatol or trotyl (in British use TNT was known as Trotyl). HE filling was initially pure TNT (1914), later TNT/Amatol mixture.
Filling weight 13 oz (368 gm)
Propellant weight 1 lb 8.8 oz (694 gm) Cordite
Total round Length 21.75 inches
375 balls, lead antimony, 41 balls to pound
Propellant weight 1 lb 6.9 oz (650 gm) Cordite
Length 21.75 inches