With the decision to bomb these skis sites in December 1943, it was also decided to plan air defences to shoot down these pilotless aircraft. The first plan envisaged the main target to be London but also recognized to the need to defend the Solent as well as Bristol, which was threatened by some launch sites in Cherbourg.
On receipt of a warning, fighters were to patrol at 12,000 feet 20 miles of the coast between Beachy Head and the South Foreland, over the coast between Newhaven and Dover, and over the Kent and Sussex between Haywards Heath and Ashfield. In addition to the fighters London was to be protected by a belt of 528 HAA guns and 804 LAA guns, sited on a line south of Redhill-Maidstone-Thames Estuary. A belt of 456 searchlights was to be set up in front of the range limit of the guns, to illuminate missiles for the fighters. Behind the guns, as a final line of defence, a barrage of 480 cable flying balloons was to be flown above the high ground between Cobham, Kent and Limpfield, Surrey.
Bristol was to be defended by 96 HAA guns, 216 LAA guns and 132 searchlights. The Solent was to be defended by 32 HAA guns, 242 LAA guns and a smaller number of searchlights.
Soon after this plan was agreed, the need for a truncated plan was required which would fit in with the large number of AA guns required for Overlord. In addition, the bombing offensive was considered to be going well against the ski sites – it was felt that the defences now only needed to provide protection against a much reduced attack from any ski sites that may survive the bombing.
The number of guns in front of London was reduced to 192 HAA and 246 LAA guns; the number of guns defending Bristol was left unchanged but it was assumed these guns would be assigned to other duties by the time of the Normandy Landings and the guns defending the Solent were removed altogether as it was considered the area would be amply protected by AA guns in the build up of the invasion forces. The guns were to found by stripping the AA defence of the North-east, North and West to a minimum. Reconnaissance for sites was carried out from March onwards and the guns instructed that they would move at a date to be decided upon and the new deployment would be known as OPERATION DIVER. An obvious gap in the defence was also pointed out at this time if the missiles flew between 2,000 to 3,000 feet instead of the predicted 6,000 feet – they would be too high for the LAA guns and too low for the HAA guns.
When the V1 offensive began, the defence plan was put into place. Eight fighter squadrons were deployed by 22nd June and 192 HAA and 192 LAA guns deployed it was known as the ‘Kentish Gun Belt’. The results were disappointing with less than 10% of missiles shot down. It was expected that results would be much better, with the missile flying on a level course and taking no evasive action. There were two main reasons for the failure. Firstly, the separation of the gun and fighter zone – fighters often broke of pursuit of the missiles too early for fear of entering the gun belt. The guns often did not open up fire soon enough due to having to be sure that the break on the radar tube was not a friendly fighter. The second problem was that mobile HAA guns could not traverse quickly enough to engage the fast flying missiles. To be effective guns would have to be static, which electrically traversed and elevated had a big advantage over mobile guns. But this seemed barely feasible with it taking weeks to construct concrete positions and the vast quantity of concrete that would be needed.
Above: Left - Kentish Gun Belt. Right - Launching areas of V1 fly bombs.
On a meeting at Fighter Command HQ’s on 13th July, it was decided to move the guns to the coast, to form a ‘Coastal Gun Belt’ belt between Cuckmere Haven and St Margaret’s Bay. The fighters could now identify the position of the gun belt by the coast line. Any missiles shot down by the guns would now fall into the sea and not on land. The move to the new gun belt began on 14th July and was completed in four days. This was some achievement involving the move of 23,000 men and women with all their kit, 30,000 tons of stores, 1,000,000 rounds of HAA ammunition; it was accomplished with the use of 8,000 Lorries and 9,000 RASC men.
The new layout included a forward fighter zone over the Channel beyond the range of the gun belt, marked by buoys and boats 10,000 yards from the coast. Thirteen day and seven night squadrons were now deployed. Aircraft also patrolled the approaches to Thames Estuary, 25 planes on patrol at anyone time. The guns were deployed in a belt along the coast 3,000 yards deep. Additions to the guns included 20 American batteries of 90 mm guns and the total number of guns deployed was now 703 HAA and 2,002 LAA guns. The Americans had also made available 165 sets of S.C.R. 584 radar which was designed to work with the B.T.L. Predictor. Once the target was picked up there was no manual operation of either the radar or predictor; the guns were also fitted with a remote-control apparatus so that fire instruments and guns worked automatically as one entity. The problem of emplacing guns in static positions quickly had been overcome by the production of a portable platform designed by the AA Command’s staff of REME under Brigadier J.A.E Burls – known as the “Pile Mattress”. The Pile Mattress consisted of a lattice of steel rails and sleepers, constructed at the REME workshops and transported in pieces to the gun site for assembly.
At about the same time of the move to the coast, a new threat was identified with some flying bombs approaching from the east. A ‘Diver Box’ defence, north and south of the Thames was hastily reconnoitered and 208 HAA and 550 LAA were deployed.
Above: Left - the Diver Defences, July 1944. Right - The Coastal Gun Belt and Diver Box
The balloon barrage, more or less in its original location was expanded and by 10th August a concentration of 2,003 balloons was flying. Between the gun zone and the balloon barrage, an inland fighter zone was operated. The searchlights, also in their original locations operated in cooperation with the fighters at night.
By 19th August, the Allied advance in France had overrun many launch sites and the westward end of the defence system could be closed down. By 5th September the rest of the launching sites in France and Belgium had been overrun by the Allied forces. From 15th June to 5th September, 8,081 flying bombs had been plotted by radar. A total of 6,090 arrived over the coast, of which 3,765 were destroyed by the combined defences and 2,325 caused incidents. Of the 3,765 destroyed 1, 903 were accounted for by fighters, 1,585 by AA guns and 276 by the balloon barrage. Casualties included 5,812 killed, 17,080 seriously wounded and 22,847 lightly wounded. Damage to property amounted to 24,000 houses damaged beyond repair and over a million damaged.
The Defence of the United Kingdom, B Collier, HMSO, 1957
The Battle of the V- Weapons, B Collier, The Elmfield press, 1964
Operation Diver, C Dobinson, CBA