The Moonlight Batteries were searchlight units of the British Army's Royal Artillery that specialised in providing 'artificial moonlight', otherwise known as 'movement light' or 'Monty's moonlight', for ground operations during the latter stages of World War II.
Early uses
Sea Navies were the first military forces to adopt the newly developed electric arc lamp searchlights (S/Ls) in the later 19th Century, to illuminate potential targets at night. Before the Bombardment of Alexandria in 1882, the Royal Navy force employed its searchlights to prove that Ahmed ‘Urabi's troops were strengthening the fortifications at night in defiance of the British ultimatum.Maurice, p. 10. Similarly, searchlights were also used to defend Ports against incursions by warships at night: in Britain this role became the responsibility of the fortress engineers and electrical engineers of the Royal Engineers (RE).Short et al, p. 14.
Land
Early in the Second Boer War, Colonel Robert Baden-Powell improvised searchlights to deter night attacks on his lines during the Siege of Mafeking. Soon afterward Major Rookes Crompton led a detachment of the Electrical Engineers Volunteers to South Africa where they operated electric arc lamp S/Ls of his own design, the first use of such equipment by the RE on campaign. They provided a primitive 'artificial moonlight' by reflecting the searchlight beams from clouds.Watson, pp. 41–4.Keith Brigstock 'Royal Artillery Searchlights', presentation to Royal Artillery Historical Society at Larkhill, 17 January 2007. Searchlight history at 873 Movement Light Squadron site. After the onset of trench warfare in World War I, the Tyne Electrical Engineers provided detachments to operate oxy-acetylene S/Ls in forward areas to assist in night defence, but these proved a failure.Short et al, p. 106.
Air World War I saw massive expansion of searchlight use in Anti-Aircraft (AA) defence to illuminate Zeppelins and bomber aircraft at night so that they could be engaged by AA guns and fighter aircraft.Short, pp. 42–200.Routledge, pp. 3–35. This became the predominant military use for searchlights between the World Wars, and in the 1930s the threat from Luftwaffe bombers in the event of war with Germany led to rapid expansion in the number of AA S/L units in Britain's part-time Territorial Army. These were frequently converted infantry battalions transferred to the RE or the RA. They formed part of Anti-Aircraft Command in Air Defence of Great Britain, but some units were also sent overseas after the outbreak of war to supplement the small number of Regular Army S/L units in defending ports, bases, airfields and other vital points.Routledge, pp. 55–67.
World War II
All the Army's AA S/L units were transferred to the Royal Artillery during 1940. Their primary role was to illuminate enemy aircraft for AA guns or night fighters to engage, although providing directional beacons for friendly aircraft was a valuable secondary role. Searchlight units scored occasional successes by dazzling enemy pilots,Digby Planck, p. 228. but attempts to set up dazzle barrages (eg a 'Cardiff–Newport Dazzle Area')37 S/L Rgt War Diary January–June 1942, The National Archives (TNA), Kew file WO 166/7787. were not particularly successful. Other uses for S/Ls were slower to emerge.
Alamein
At the time of the Second Battle of El Alamein, the British Eighth Army had two troops of the London Electrical Engineers under its command for area AA protection, but five of their lights were used to assist advancing Allied troops in direction-keeping during Operation Lightfoot, the night attack that launched the battle. No attempt was made to illuminate the sky (the battle was fought in full moonlight, though this was much obscured by dust).Joslen, pp. 566, 576.Pitt, p. 298.
Sicily & Italy Battlefield illumination was also used in the campaigns in Sicily and Italy up to and including the Gothic line. It was used to illuminate the battlefield for not only infantry attack but also, because of the ridge nature of the terrain, catching out German Artillery in the full glare of light on the opposite slopes. Careful reconnoitring of the area and individual placement achieved excellent results. The 1st Canadian Group had with them 422nd S/L Battery who undertook this task successfully.Jackson, p. 290.
Normandy By the time of Operation Overlord and the Normandy campaign in the summer of 1944 the Luftwaffe was greatly weakened, and the use of radar by AA guns and night-fighters was widespread, so the S/L units in 21st Army Group were under-employed. Some lights from 474th S/L Battery were given a subsidiary coast defence role to protect the anchorages from E-Boat attacks.101 Sub-Area Notes, 18 March 1944, TNA file WO 171/1085. By late August, as 21st Army Group broke out of the beachhead, enemy night air raids were rare and 557th S/L Bty was used to provide floodlighting for round-the-clock bridge-building by the Royal Engineers; this soon became a routine task for S/L units.557 S/L Bty War Diary July–December 1944, TNA file WO 171/1214. As the advance across France gathered momentum, newly arrived batteries of 41st and 42nd S/L Rgts found themselves providing security lighting for Prisoner of war (PoW) camps.80 AA Bde War Diary 1944, TNA file WO 171/1085.
The major new use for S/L units in this campaign was to reflect light off the cloudbase to provide 'artificial moonlight' or 'movement light' (also known as 'Monty's moonlight' after 21st Army Group's commander, General Sir Bernard Montgomery) in support of night operations. 344th, 356th and 474th Independent S/L Batteries pioneered this technique using their mobile 90 cm searchlights.Routledge, pp. 314, 317. On 9 July, 474 Bty sent six S/L detachments to provide artificial moonlight in the forward area for 43rd (Wessex) Division, which was moving up to its starting positions for Operation Jupiter. Three days later, the battery repeated the process for 53rd (Welsh) Division.474 S/L Bty War Diary, June–December 1944, TNA file WO 171/1213.Ellis, p. 315.
The technique was next used operationally to assist the assembly of troops for Operation Greenline on the night of 14/15 July, when the drivers of 15th (Scottish) Division 'found the light a great help to them in finding their way up the pot-holed track through the blinding dust'.Martin, pp. 66–9. The S/L positions were subjected to light retaliatory shelling and mortar fire and to low-level air attack, suffering some casualties. However, during the fighting the following night, a jammed column of troops and vehicles was dangerously silhouetted in the movement light, while elsewhere a smoke cloud blotted it out.Martin, p. 71–5. Nevertheless, from then on the S/L batteries were regularly called upon to send detachments to provide movement light to support British and Canadian formations as the Battle for Caen progressed This innovation in 21st Army Group narrowly preceded similar experiments by Eighth Army on the Italian front.
On 7/8 August, 344th S/L Bty provided lighting for II Canadian Corps' night attack south of Caen (Operation Totalize); officers of the newly arrived 557th S/L Bty attended to gain experience in this new technique.344 S/L Bty War Diary June–December 1944, TNA file WO 171/1207.
The advance After 21st Army Group broke out of its Normandy beachhead, 557th S/L Bty went to Le Havre where it provided artificial moonlight for the attack by I Corps on the night of 10/11 September (Operation Astonia). Here the technique proved particularly valuable for ensuring safe passage through gaps cut in the minefields. The battery then went on to provide lighting for the continued fighting in the town and docks.Routledge, p. 317.Doherty, p 108.
In October, 557th S/L Bty joined II Canadian Corps in the Battle of the Scheldt (Operation Switchback), providing 'moonlight' for the attack on South Beveland and AA defence for the Canadian gun lines.76 AA Bde War Diary, 1944, TNA file WO 171/1084. Afterwards, it joined 344th, 356th, and 474th Btys in providing light for bridge and airfield construction, and AA defence for the bridges at Grave, Mook and Nijmegen that had been captured during Operation Market Garden. At Nijmegen the two vital bridges were under regular attack from the air and from frogmen with explosive charges, so that searchlights had to sweep the river as well as the sky.557 S/L Bty War Diary October–December 1944, summary at RA Netherlands.Routledge, p. 325, Table LII, p. 331–2.
On 4 November C Troop of 356 S/L Bty was detached to 51st (Highland) Division for its first experience with artificial moonlight. This was for an assault crossing of the Afwateringkanal and River Maas and subsequent bridgelaying. The troop stayed on to illuminate bridge repairs on the second night. After a difficult move, with several vehicles ditched, the troop was repositioned to join 474 S/L Bty in supporting a night move by 154 Bde into Nederweert on 9 November, during which the troop suffered minor damage from enemy shellfire. After a few nights providing movement light over canal and river bridges, XXX Corps sent C Troop to assist 84th US Division in its attack on Geilenkirchen as part of Operation Clipper. During the preparation period the S/Ls were exposed each night 'to fox the Boche' with 'stooge' beams in different directions. The attack went in at 04.00 on 18 November and the troop provided artificial moonlight until 07.00 to help the Flail tanks and engineers to breach the defences. The following night the troop assisted 43rd (Wessex) Division in the continuing attacks on the Geilenkirchen salient, receiving a retaliatory air raid that caused no damage. Heavy rain fell from 20 November onwards, and finding suitable S/L positions in the mud and minefields was difficult. Eventually the Troop deployed on a Hitler Youth campsite and at the railway station. As 84th Division's operation continued with the capture of Tripsrath, the lights attracted increasing amounts of enemy shellfire, causing minor casualties and damage. On 23 November the S/Ls were doused for a while to allow stretcher bearers to bring in the wounded. On 24 November a US S/L unit arrived to be briefed on the artificial moonlight technique, and the following day C Troop left 84th US Division and rejoined 43rd (Wessex) to resume routine movement light duties.356 S/L Bty War Diary 1944, TNA file 171/1208.
Experiments Early in 1945, in preparation for the forthcoming attack in the Klever Reichswald (Operation Veritable), 31st (North Midland) Anti-Aircraft Brigade HQ in Belgium carried out experiments to optimise artificial moonlight techniques to provide lighting for night movement of ground troops, for floodlighting their objectives and for dazzling the defenders.
At the end of January 1945, 557th S/L Bty under First Canadian Army command began experiments to put a searchlight onto a Canadian Ram tank with its turret removed, with the electrical generator carried in a second accompanying tank. (The obsolete Rams were also being used as turretless armoured personnel carriers known as Kangaroos.) A section of 557 S/L Bty based at Nijmegen began operating these vehicles in February in support of 15th (Scottish) Division.557 S/L Bty War Diary 1945, TNA file WO 171/5103.