ROYAL ARTILLERY Artillery was a large arm which encompassed field artillery (field, medium, heavy and super heavy), anti aircraft artillery (light, heavy and searchlights), anti tank artillery and a comprehensive survey, fire control and command system. ROYAL ARTILLERY CONTENTS Field Artillery Royal Artillery Headquarters in an Infantry Division. War Establishment II/117/3. January 1944 Royal Artillery Headquarters in an Infantry Division. War Establishment II/117/4. March 1945 Royal Artillery Headquarters in an Armoured Division. War Establishment II/104/2. December 1943 Royal Artillery Headquarters in an Armoured Division. War Establishment II/104/3. March 1945 Headquarters Army Group Royal Artillery. War Establishment II/117/3. January 1944 Headquarters Army Group Royal Artillery. War Establishment II/117/4. March 1945 Field Regiments Field Regiment War Establishment II/190B/1. December 1943 SP 105mm Battery War Establishment II/189/1. August 1943 Field Regiment SP 25 pdr. War Establishment II/190A/2. May 1944 Field Regiment SP 25 pdr. War Establishment XIV/540/1. March 1945 Medium Regiment War. Establishment III/10/5. January 1944 Heavy Regiment. War Establishment III/220/2. January 1944 Headquarters Super Heavy Group. War Establishment III/328/1. Super Heavy Regiment (Road). War Establishment XIV/523/1. August 1944. Super Heavy Battery (Rail) 18” Howitzer, Cadre. War Establishment XIV/524/1 August 1944. Headquarters Mountain Regiment. War Establishment III/234/1. April 1943. Mountain Battery. War Establishment III/235/1. April 1943 Survey Regiment. War Establishment III/13/8. November 1943 Air Observation Post Squadron. War Establishment III/126/4. October 1943 Counter Mortar Increment HQ Infantry Divisional RA. War Establishment XIV/420/1. July 1944. Counter Mortar Officers Staff (Armoured Division). War Establishment XIV/432/1. September 1944. Counter Mortar Officers Staff (Armoured Division). War Establishment XIV/432/2. February 1945. Counter Mortar Officers Staff (Infantry Division). War Establishment XIV/434/1. September 1944. Counter Mortar Officers Staff (Infantry Division). War Establishment XIV/434/2. February 1945. Corps Sound Ranging Troop. War Establishment XIV/431/1. September 1944. Army Radar Battery. War Establishment XIV/452/1. September 1944. Divisional Counter Mortar Battery. War Establishment II/190E/1. December 1944. Artillery Range Detachment. War Establishment XIV/435/1. January 1945. Calibration Troop WE III/13A/3 Field Rocket Battery (Cadre). War Establishment XIV/456/1. February 1945. Combined Operations Bombardment Troop. War Establishment XII/140/1. October 1943. Antitank Artillery Headquarters Anti Tank Regiment. War Establishment II/181/2. January 1944 Anti Tank Battery, Infantry Division. War Establishment II/186C/1. January 1944 Anti Tank Battery, Assault Division. War Establishment II/190/2. January 1944 Anti Tank Battery SP, Armoured Division. War Establishment II/188/2. January 1944 AT Battery Towed, Armoured Division. War Establishment II/186/1. April 1943 Headquarters Anti Tank Regiment, Infantry Division. War Establishment XIV/473/1. March 1945. AT Battery 21 Army Group. War Establishment XIV/470/1. October 1944 AT Battery 21 Army Group. War Establishment XIV/471/1. January 1945 AT Battery 21 Army Group. War Establishment XIV/472/1. January 1945 Headquarters of a Corps Anti Tank Regiment. War Establishment III/308/1. February 1944 Anti Tank Battery, 3” M10 SP. War Establishment III/309/1. February 1944 Anti Tank Battery, 17dr track towed. War Establishment III/310/1. February 1944 Anti Aircraft Artillery Headquarters GHQ Anti Aircraft Troops. War Establishment XIV/151/2. December 1944 Anti Aircraft Defence Headquarters. War Establishment XIV/450/1. June 1944 Identification Troop. War Establishment XIV/433/1. November 1944 Local Warning (Radar) AA Troop. War Establishment XIV/454/1. November 1944. Group Control Centre AA Liaison Unit. War Establishment XIV/457/1 Group Operations Room AA Liaison Unit. War Establishment XIV/458/1 AA Practice Camp. War Establishment XIV/453/1. October 1944 AA Practice Camp. War Establishment XIV/453/2. March 1945 Heavy Anti Aircraft Battery, 3.7” mobile. War Establishment III/219/2. August 1944. HQ Mixed Heavy AA Regiment, 3.7” Static, Overseas. War Establishment III/332/1. November 1944 Mixed Heavy Anti Aircraft Battery, 3.7” Static, Overseas. War Establishment III/333/1. November 1944 Headquarters of a Divisional LAA Regiment. War Establishment II/179/2. November 1943 Headquarters of a Corps LAA Regiment. War Establishment III/170/1. July 1942. Light Anti Aircraft Battery. War Establishment III/171/1. July 1942 Light Anti Aircraft Battery Mobile. War establishment XIV/455/1. October 1944. Light Anti Aircraft Battery Mobile. War establishment XIV/459/1. March 1945 Light Anti Aircraft Battery PDA. War Establishment XIV/451/1. June 1944 Headquarters Searchlight Regiment (Mobile). War Establishment XIV/562/1. September 1944 Searchlight Battery (Mobile). War Establishment III/191/2. March 1944. Searchlight Battery (Mobile) 21 Army Group. War Establishment XIV/563/1. September 1944. Searchlight Battery (Moonlight) 21 Army Group. War Establishment XIV/564/1. February 1945 HQ Searchlight Regiment (Defended Port Abroad). War Establishment XIV/560/1. May 1944 Searchlight Battery (Defended Port Abroad). War Establishment XIV/561/1. September 1944 Equipment Guns Ammunition Radars Vehicles are described under the relevant sections: Field Artillery Anti Aircraft Artillery Anti Tank Artillery. THE GUNS. By 1944/45 the Royal Artillery had a good armoury of guns of all types. Most were introduced into service during the war and so were up to date, state of the art equipments. Some were US designed and manufactured. FIELD ARTILLERY. 25pdr The 25pdr field gun the standard field gun of the British Commonwealth and was possibly the best all round field gun of its era. - The MkII gun fitted on the MkI carriage was the standard type. It was introduced in 1940 and remained virtually unchanged throughout its long service. - The MkIII gun was the MkII with minor modifications to the breach to assist loading at high elevations. All 25pdrs in NW Europe were fitted with muzzle breaks designed to reduce recoil when firing anti tank rounds with super charge. The 25pdr was more correctly a gun/howitzer since it could be fired at low elevation as a gun and at high elevation, 40 degrees, as a howitzer. This allowed it to drop shells behind hills or other obstacles. The use of variable charges made it even more versatile. Traverse was limited to 4 degrees either side but the gun was usually fired from its turntable. This could be carried on the tractor or under the gun itself. When the centre of the turntable was fixed to the pivot on the gun, and the gun wheels sited on the outer rim of the turntable, a traverse of 360 degrees could be achieved with minimum effort. The maximum range was 13,400 yards. The crew was six men. - No 1 was a sergeant who commanded the gun detachment. - No 2 operated the breech - No 3 was the gun layer. He sat on the left hand side and controlled both the gun laying (using a dial sight) and the elevation (using a sight clinometer) - No 4 was the loader who loaded shell and charge after showing them to the No1 - No 5 passed ammunition to No4 - No 6 was stationed at the limber to unload ammunition from the trays and select the correct charge. The ammunition. The 25pdr used separate charges. The shell was loaded into the gun breech and was followed by the propelling charge in a brass case. This allowed a variety of charges to be used. This was useful at higher elevations. The standard brass case contained three bags of propellant and the charge was varied by removing bags. - Charge 3 used all three charges - Charge 2 had one charge removed - Charge 1 had two bags removed. The third charge could not be removed. - Supercharge. It was possible to add a further bag to produce a supercharge. The extra charges were carried on the tractor. In addition there was an incremental charge for anti tank firing. This was also added to the charge case. The incremental charges and anti tank shells were carried on the tractor. There was a variety of shells for various tasks. - High Explosive. This was by far the most common and made up most of the loads of the limbers. - Smoke. A proportion of smoke shells were carried in the limber. - Armour Piercing. These were solid anti tank shot and were carried in a steel case in the crew compartment of the tractor. In NW Europe they were for emergency use only and seldom employed. The following were available but were not normally carried on the limber or tractor. - Coloured Smoke. These could be used for marking targets and forward locations. - Target Recognition. These were much as for Coloured Smoke but were illuminated for use at night. - Chemical. These were stocks of gas shells held in case of need. None were issued to units. - Incendiary. These were produced in response to a requirement in Normandy for a means of setting fire to crops which could hide enemy positions. It was the winter of 1944 before they appeared and the campaign was over before the next crops could grow. The standard shell came with a direct action or impact fuse. These could be removed and replaced with delayed action or time fuses if required. Fuses were carried on the tractor. Shells came in a box of 4. Charges came in a box of 8. All ammunition in the limber was carried in two round trays. Two shells and two charges per tray. After an engagement there was a considerable amount of salvage which had to be collected and returned to ordnance ammunition units. This was carried by returning ammunition lorries. Salvage included that at the gun position which was the charge bags removed from the standard cases and all used brass cases. At the wagon lines it included all the ammunition unpacked from boxes but not loaded onto limbers and all empty ammunition boxes. 3.7” Howitzer. The 3.7” howitzer was mounted on a carriage with a split trail. It had an elevation of 42 degrees and a traverse of 20 degrees either side. It was designed for carriage on pack animals but was adapted for towing behind vehicles. In 21 Army Group it was fitted with pneumatic tyres and towed by a jeep. An ammunition limber had been produced but was not used with jeeps. A gun shield could be fitted but was often omitted to save weight. The 3.7” howitzer was also carried on major warships for use by landing parties. The crew was six in the towed role No 1, commander No 2, breech operator No 3, layer No 4, loader No 5, ammunition number No 6, ammunition number Being a howitzer it used separate ammunition. Range could be determined by varying the charge as well as elevation. Ranges were as follows. Charge 1. 2,277 yards Charge 2. 2,788 yards Charge 3. 3,641 yards Charge 4. 4,560 yards Charge 5. 6,000 yards Super. 6,800 yards. 5.5” and 4.5” guns. The 4.5” and the 5.5” were mounted on the same carriage and were identical except for the barrel length and calibre. The barrel from one could be fitted to the carriage of another with only small adjustments to the recoil system. Elevation was 45 degrees and traverse was 30 degrees either side. The 4.5” had a range of 20,500 yards with a 55lb shell The 5.5” had a range of 16,200 yards with the standard 100lb shell but when an 80lb shell was introduced in conjunction with a super charge the range was 18,100 yards. In action the 4.5” weighed 12,880 lb and the 5.5” weighed 13,646 lb. This made them difficult to manhandle into position. Fortunately they were not usually called on to move position frequently and their traverse was sufficient for most tasks. The gun crew was 10 men. The propelling charges for the 5.5” were bagged. There were four separate charges which could be used in combination to give the required range. The basic Charge 1 was a potato masher shape. Charge 2 could be slipped over the shaft of Charge 1 and together these made the short range portion. Charge 3 was a cylindrical bag to which Charge 4 could be tied. These two made the long range portion. Only Charges 1 and 3 had igniters so that charges 2 and 4 could not be fired separately. The Super Charge for the 80lb shell came as on piece and could not be divided or used in conjunction with other charges. The propelling charge for the 4.5” gun was similar and came in three parts. Charge 1 was a potato masher shape and Charge 2 fitted over the shaft. Charge 3 was a cylindrical bag which could be ties on top of Charge 2. 7.2” Howitzer Mks 1 to 4. Few of these heavy guns were used in 21 Army Group and those that were used were replaced fairly early in the campaign. The 7.2” Howitzer in this form was basically a WWI weapon. Originally produced as an 8” Howitzer numbers of those surviving in 1940 were reworked by removing the barrel liners and fitting new 7.2” liners instead. This gave a greater range but the old WWI box trail carriage was not really adequate. When fired the recoil was too great to be absorbed by the recoil mechanism and the carriage leapt backwards, and sometimes sideways. Large scotches were placed behind and in front of the gun wheels in order to control the recoil. Ammunition was as for the 7.2” Mk6 described below, but charge 4 was not used. Maximum range was 16,900 yards. Mk1 was a conversion of British barrels. Mks 2 to 4 were conversions of similar US weapons. 155mm gun and 7.2” Mk6 Howitzer. The US 155 mm carriage was used in conjunction with a two wheel limber to support the trail when moving. In firing position the limber was removed and the carriage suspension was lowered so that the trail lay on the ground thus providing a firm platform. The gun could be elevated to 63 degrees and be traversed 30 degrees either side. The 155mm M1 gun fired a 95lb shell to a range of 25,395 yards. The propellant charge came in two parts, a base charge and a super charge. The British 7.2” Mk6 gun was a new design fitted to the same carriage as the US 155mm. It fired a 200lb shell to a range of 19,600 yards. The propellant charge came in two forms. - There was a four part charge which could be used in increments. Charge one was a potato masher shape and Charges 2, 3 and 4 were hollow cylinders which could be slipped over the shaft of Charge 1. - There was a Super Charge which was a single bag charge which replaced the others. Gun crews were 13 men in each case 240mm Howitzer and 8” gun. The large 240mm howitzers were well thought of but were relatively little used. This was partly because there was little opportunity to deploy siege artillery and partly because tactical air power did the job better. The 240mm Howitzer fired a 360lb shell Maximum range was 25,225 yards. A reduced charge was available which gave a maximum range of 8,450 yards. Maximum elevation was 65 degrees Traverse was 20 degrees either side Very few of the big 8” guns were made and issued. They were not very accurate and the wear on the barrel was excessive. The 8” gun fired a 240lb shell Maximum range was - 30,315 yards using Normal Charge - 35,635 yards using Super Charge - 8,450 yards using Reduced Charge Maximum elevation was 50 degrees Traverse was 20 degrees either side The 8” gun and the 240mm howitzer used the same carriage. Both guns were so heavy that they each had to be broken into two loads, each with its own transporter. The barrel and recoil system were carried on one carriage and the trail on the second. Each was towed by a M6 38ton fully tracked tractor. Fully loaded each carriage weighed some 50,000 lbs. The ANTI TANK GUNS. 6pdr Tanks developed rapidly during the war and so anti tank guns had to develop to match them. The 6pdr was delayed by the need to keep the older 2pdr ant tank gun in full production after the Fall of France. When it was introduced it had a short barrel since this could be produced more rapidly on the available machinery. The gun used in NW Europe was the longer barrelled version. Data: Calibre 2.244 in Maximum Range 5,500 yards Armour Penetration 74mm at 1000 yards Weight of Gun and Carriage 2,521 lb Drill. The 1944 drill handbook for the 6pdr AT gun gives the following detachment Number 1 Gun Commander Number 2 Loader Number 3 Layer Number 4 Second in Command Number 5 LMG gunner and lookout. The gun was unhooked from the tractor which then retired to the wagon lines. The gun was then finally positioned by manpower. Number1 guided the muzzle and coordinated the effort Numbers 2 and 3 lifted the trail using a hand spike Numbers 4 and 5 fitted drag ropes, normally carried on the front of the shield, to the eyes on the wheel hubs. In action - Number 1 took up a position to one side of the gun. Ideally he should be able to see clearly while remaining under cover. He identified targets and gave the order to lay the gun using the clock system where 12 o clock was directly ahead. He also estimated the range and deflection. - Number 2 knelt to the right side of the breech on his left knee. He loaded the gun and reported ‘In’. - Number 3 knelt on the left side of the breech on his right knee. He laid and actually fired the gun. - Number 4 crouched behind Number 3. He relayed orders from Number 1 and also approximately aimed the gun and set the range on the range scale. - Number 5 was available as required. 17pdr This turned out to be one of the best all round guns of the war. It was rather heavy but so were all guns of the same class. They could not stand the force of the recoil if they were not on sturdy carriages. Data: Calibre 3in Maximum Range 10,000 yards Armour Penetration 231mm at 1000 yards Weight of Gun and Carriage 6,537 lb The drill for the 17pdr was almost identical to that for the 6pdr except that there were two extra gun numbers, 6 and 7, who were ammunition numbers in action. When positioning the 17pdr Number1 guided the muzzle and coordinated the effort Numbers 2 and 3 were to the rear of the shield Numbers 4 and 5 lifted the trail using a hand spike Numbers 4 and 5 were on the drag ropes ANTI AIRCRAFT GUNS 3.7” Heavy Anti Aircraft Gun. The 3.7” AA gun was a very advanced weapon when first introduced into service in 1936 and continued to be improved until production ceased in 1945. The basic gun fired a 28lb high explosive shell to a ceiling of 40,000 feet although the effective ceiling depended on the fuse, predictor and fire control being used. For serious anti aircraft work in 1944/45 the gun was linked to Radar No3 MkV, Molins No11 fuse setter and Predictor No10 which left the crew little to do but lift shells onto the loading tray. 25 rounds a minute could then be achieved. When variable time, or proximity, fuses were used the Molins fuse setter was not used and the rate of fire was 32 rounds per minute. The mounting, while mobile, could be jacked down and stabilised to provide a very secure base. For rapid deployment the rear wheels could be left on and raised on davits. More usually all wheels were removed to give a clear working area. Traverse was 360 degrees and elevation was 80 degrees. When loading was by hand a respectable 10 rounds per minute could be maintained. Heavy Anti Aircraft Artillery Regiments were increasingly used in a field artillery role. As the Allies gained air superiority there was little work for such units. The alternative was to convert the Heavy Anti Aircraft units to Field regiments, or even to infantry which was much in demand. There was therefore some pressure on them to find a new role. They could readily return to their primary task if the enemy came up with a new weapon as they did with the V1 attacks on Rotterdam. The high velocity and flat trajectory of the Heavy Anti Aircraft gun was the opposite of the heavy guns of the Army Group Royal Artillery, and the shells used fixed charges so that shells could not be lobbed. This made accurate ranging against ground targets difficult and the zone in which shell landed would be long and narrow. At first there were no sights suitable for ground fire but these were issued in late 1944 and with suitable tables gunners could engage ground targets with reasonable success. The guns were heavy and difficult to emplace but once they were emplaced they could engage targets rapidly using their all round traverse and electronic fire control. One great advantage was the high rate of fire. The 3.7” AA gun proved very useful in the counter battery role. The shells were rather light but their considerable range and high rate of fire, coupled with air burst time fuses made them ideal for suppressing enemy fire. They might not destroy the enemy guns but they could clear the gun site of personnel and spoil their concentration. The 3.7” air bursts were also very effective against personnel and vehicles in the open. An added advantage was that the high velocity meant that the shells arrive without warning. The AA 3.7” gun had a horizontal range of 20,600 yards but because of the flat trajectory this had to be in line of sight, with no obstacles between the gun and the target. The shell weighed 28lb The standard charge was 8lb 8oz in a brass case fixed to the shell. A reduced charge was available for firing against ground targets. An anti tank round was available for self defence. The Bofors 40mm Light Anti Aircraft Gun. Designed in Sweden the Bofors 40mm AA gun was used by many armies including Britain and the USA. It was also used by several navies. The gun was intended for use against low flying aircraft and was automatic. Shells were loaded in four round chargers and then loaded into the breech by a spring rammer. Empty shell cases were ejected to fall down a chute which threw them clear. The gun was balanced by springs and mounted on a ball race so that it was quick and easy to train and aim by hand. The carriage was fitted with outriggers and could be leveled and stabilised by jacks. It could be fired from its wheels in an emergency. Elevation was 90 degrees and traverse was 360 degrees so that the gun could cover the entire sky. Weight in action was 4,368 lb which just about made it possible to manhandle it. Rate of fire was 120 rounds a minute. The horizontal range was 10,800 yards and the maximum ceiling 23,000 feet. In practice however the effective ceiling was 5000 feet which was dictated more by the sights than the gun. Fixed ammunition was used, with the propelling charge being in a brass case. The standard shell was Shell HE Mk4T which weighed 2lb and had a tracer/igniter. This allowed the path of the shell to be followed and the shell detonated at a range of either 3,400 yards or 5,500 yards. Unlike the heavy AA shells which were fused to detonate in the path of an aircraft the Bofors shell self destructed to avoid a rain of shells coming down on friendly ground troops. There was also a useful armour piercing projectile, Shot AP Mk6T Polsten 20mm AA. Not usually listed as an artillery piece the Polsten 20mm was an automatic cannon developed from the Oerliken for close air defence in units. Small numbers were manned by the Royal Artillery. Some 20,000 were produced in 1943/44 when it was thought that the Bren gun was too light for the protection of units and convoys. In its standard form it was mounted on a two wheeled carriage towed by a unit vehicle. Most front line units had some on the establishment but they were seldom used and soon withdrawn. It is probable that none of the towed version even went to France. A 15cwt self propelled mounting was developed. Originally this was on a Bedford MW with a simple platform body on which a complete Polsten and carriage was mounted. The wheels were removed and stowed on brackets. There was ammunition stowage behind the cab and a bar prevented the gun from firing into the cab. These do not seem to have been used operationally. However for D Day a number of Polsten were mounted on CMP 4 X 4 15cwts. These had the GS body removed and a Polsten platform body added. The gun could be dismounted and an ammunition trailer could be towed. Polstens were mounted on redundant tank chassis for use in armoured units. Twin Polsten were mounted in a specially designed turret mounted on a Centaur to become Centaur AA MkII or on a Crusader to become Crusader AA MkIII. Redundant Polsten were mounted on LVTs for the Rhine Crossing. The Polsten used 60 round drums of ammunition, usually a mix of high explosive, tracer, incendiary and armour piercing. It could fire at the rate of 460 rounds a minute and the normal range was about 1000 yards. AMMUNITION. The shell is the real weapon of the Royal Artillery, the gun being the means of delivering it. Most guns had a variety of projectiles so that a clear system of marking and identifying them was required. Some of the markings are for the user, the loader and ammunition numbers, and some for those who must store and maintain it, the RAOC depots. All shells are painted to preserve them from corrosion so it is logical to paint the main types in different colours. High Explosive shells were painted buff. Smoke shells were painted a light green Flare and Star shells were painted white Incendiary shells were painted dull red Chemical shells were painted grey Armour Piercing shells, and all others, were painted black The following markings were more concerned with storage, maintenance and issue Red ring near the nose indicates an explosive filling (even if only a tracer). Green band round the shoulder indicates TNT or Amatol explosive. Blue Band round the shoulder indicates RDX explosive Red star on shoulder indicates a star shell. Stencilling was also applied in the following order starting at the nose Calibre and Mark of gun Series number indicating filling lot Code number indicating method of filling Chemical shells were not used but were held in theatre and marked as follows Green band on a grey shell indicated a non persistent toxic gas Two green bands on a grey shell indicated a persistent toxic gas Red band on a grey shell indicated a non persistent irritant gas Two red bands on a grey shell indicated a persistent irritant gas RADAR Anti Aircraft Radar. Anti aircraft artillery used several radars belonging to several generations. Development of radar was rapid and dramatic. There were still some older long wave sets in service. Newer microwave sets were the norm for gun laying, and the new US built radar was in a new class altogether. Radar AA No3 MkII. Radar AA No3 MkII was the standard gun laying set in 1944, being a 10cm mobile radar for the accurate fire control of heavy anti aircraft guns. It was mounted on a four wheeled trailer with twin rear wheels and three point jacks. There was on jack in the centre of the rear of the chassis and two folding arms at the front. A steel cabin mounted the aerials and contained the display units. Two four foot parabaloid aerials were mounted on a rotor unit which could be rotated 360 degrees. The aerial dishes could also be tilted on the rotor arm. The control cabin contained two 6” display tubes, one for course range and one for fine range. The target could be selected on the coarse range tube and the range then determined for the fine range tube. It could transmit continuous information the range, bearing and elevation to a predictor, which could then further transmit information to individual guns. It was in volume production in 1943 and by April 1945 876 sets had been delivered, including 50 for Russia. This radar was used in conjunction with Radar AA No1 MkII or Radar No4 MkII which were early warning and tracking sets. (see below). Radar AA No3 MkII was also used for counter mortar work. Radar AA No1 MkII. This was an older but reliable set for early warning and continuous tracking. It was in fact a two vehicle set, each set being mounted on a trailer. Operating on 5m wavelength it had a transmitter on a rotating house body, and a receiver on a similar body. Information was transmitted to the radar No3 MkII control cabin, together with IFF information, so that targets could be selected. Radar AA No4 MkII. This was a light warning set and putter on. Sets were mounted in house type bodies on 15 cwt trucks. They used compact yagi aerial displays and were accurate but lacked the range of the No1 MkII radars. Aerials were roof mounted and could be rotated 360 degrees. When used with Radar AA No3 MkII it was located near to the larger set and transmitted information to it by cable. Similar sets were also used for early warning and these carried a Wireless set No22 for reporting to a control centre. Radar AA No4 Mk5 This was a special version of which twenty two were produced in May and June 1944 for 21 Army Group, presumably for use in the D Day landings. They seem to have been as for No4 MkII but with provision for tactical control. Radar AA No3 MkV. This was the US SCR 584 set. When linked with electronic Predictor No10 this radar was capable of continuously plotting a target with great accuracy and speed. In order to take full advantage of this new equipment the Predictor nor only sent information direct to the guns but used electric power to remotely aim and lay the gun, set the fuse, load the shell and finally fire the gun. This solved the problem of variation in crew performance and manpower was now only needed to lift the shells into the power loader. Counter Mortar Radars. Redundant radar sets were used for the rapid location of mortars. The mortars were highly mobile and a rapid response was needed. Radar AA No3 MkIII There were a considerable number of Radar AA No3 MkII sets available since there was little work for AA artillery and many Heavy AA Regiments were formed into infantry battalions. With very little modification these radar sets could be used to locate mortars. The radar was then Radar AA No3 MkII (F). The moment a mortar round left the tube it became visible on the radar and its bearing and range could be determined very quickly. The most accurate use was when it was linked to a 3 pen Westex Recorder which took bearings from three radars and plotted them. Bearings and range from a single radar was still accurate to 150 yards. These radars and associated equipment were used in Divisional Counter Mortar Batteries. The recorder was carried in a house bodied Austin K5 4 X 4 3ton lorry. This radar could also be used for tracking meteorological balloons used for the production of the artillery ‘meteor’ (meteorological) telegrams. Radar AA No3 MkV This was much more accurate than the Radar AA No3 MkIII. It was the US SCR 584 which was a very advanced equipment for its day. It was still required for anti aircraft work but some were made available for counter mortar work. In its primary role it could locate and automatically track aircraft and use an integral computer (Predictor Mk10) to work out the big sums needed to predict where an aircraft would be when a shell arrived. It could also control a battery of anti aircraft guns. Each gun automatically followed the radar and fired remotely under radar control. Much of this was redundant in a mortar locating radar but its ability to track incoming rounds, and to do the necessary calculations made location both quick and accurate. The whole equipment was mounted in a box semi trailer. In theory Radar AA No3 MkV could locate and fire direct onto moving ground targets. The US Army did so on one occasion. Radar FA No3 Mk2. The most practical counter mortar radar came just too late for service in WWII. This used a US airborne radar which was light and accurate. Carried in a trailer towed by a halftrack it was very mobile and the dish could be mounted separately. It was trial mounted on an artillery observation tower. Weighing only 600lbs it used only a 1.2KVa generator. The crew in the halftrack included two operators and a plotter with artillery board. Field Artillery Radar. It was possible to use any of the anti aircraft radars for accurate location of enemy artillery by having a spotter aircraft fly over the site and have the radar track it. The pilot only needed to signal when he was directly overhead the target and the exact location could be worked out very quickly. Radar CA No1 Mk4 (F). Another use of redundant radar was for ranging artillery fire. Radar CA No1 Mk4 was a 3cm wavelength Coastal Artillery radar set used to spot the fall of shell in coastal batteries. Mounted on a trailer it was used to observe shell bursts up to 20,000 yards away. This allowed artillery fire to be controlled well beyond the range of observers and in all conditions. It also allowed the engagement of moving targets. As used in 21 Army Group it became Radar CA No1 Mk4 (F). Power supply was a trailer mounted 15KVa generator. Radar FA No1 Mk4 (F). This was developed from Radar CA No1 Mk4 (F). It was mounted on a half track with a large house type body accommodating three operators. The aerial array was roof mounted. Performance was as for the CA set. Power supply was from a 6.25KVa generator carried in a trailer.