Mobilisation In June 1939, as the international situation worsened, a partial mobilisation of the TA was begun in a process known as 'couverture', whereby each AA unit did a month's tour of duty in rotation to man selected AA gun positions. Full mobilisation of AA Command came in August 1939, ahead of the declaration of war on 3 September 1939. 37 AA Brigade deployed and operated a gun layout from
Dagenham to
Thorpe Bay in
Essex, along the north side of the
Thames Estuary, known as 'Thames North'. This had a planned layout of 20 HAA sites, however only half were occupied by September 1940. Opportunities for action were rare during the
Phoney War, but on the night of 22/23 November 1939 the HAA guns of Thames North combined with those of
28th (Thames & Medway) AA Bde on the other bank of the estuary ('Thames South') to engage at least two enemy mine-laying aircraft that had strayed into the mouth of the Estuary. One wrecked aircraft was found on the marshes. On 1 June 1940, all RA units equipped with the older
3-inch or newer
3.7-inch AA guns were designated as Heavy AA (HAA) regiments to distinguish them from the newer Light AA (LAA) regiments appearing in the order of battle. . On 15 September, remembered as the climax of the battle, 220 bombers attacked London in the morning despite heavy casualties inflicted by the RAF fighters. More attacks came in the afternoon and the AA guns around London, particularly 37 AA Bde, were continuously in action, breaking up the bomber formations. Between the guns and fighters, the
Luftwaffe lost 85 aircraft that day, an unsustainable rate of loss.
The Blitz After 15 September, the intensity of Luftwaffe day raids declined rapidly, and it began a prolonged night bombing campaign over London and industrial towns (
The Blitz). This meant that the Thames North and South AA guns were in action night after night as the bomber streams approached the London Inner Artillery Zone, but even with the assistance of searchlights, the effectiveness of HAA fire and fighters was greatly diminished in the darkness. By November, 90th HAA Rgt had been transferred across the estuary to reinforce 28 AA Bde in Thames South. This had a planned layout of 25 HAA sites (of which only 16 were occupied) running from
Dartford to
Chatham, Kent, where there was a strongly defended area around the naval dockyards at Chatham and
Sheerness and the aircraft factory at
Rochester. This was controlled from a Gun Operations Room (GOR) at Chatham. As well as bomber streams passing over towards the London Inner Artillery Zone (IAZ), the Chatham area was also subjected to minor attacks.
Mid-war artillery tractor towing a 3.7-inch HAA gun on exercise at
Burrow Head in Scotland, 18 February 1944. The Blitz ended in May 1941 but 90th HAA Rgt remained in 28 AA Bde for the next year. It had sent a
cadre to 205th HAA Training Regiment at
Arborfield to provide the basis for a new 394 Bty; this was formed on 12 December 1940 and joined the regiment on 17 March 1941 • RHQ • 272, 284, 285 HAA Btys • 90 HAA Signal Detachment,
Royal Corps of Signals • 90 HAA Workshop,
Royal Electrical and Mechanical Engineers By July, 90th HAA was designated as a mobile regiment in
21st Army Group, training for the planned Allied invasion of Normandy (
Operation Overlord).
North West Europe , August 1944. Operation Overlord began with
D Day on 6 June 1994, but in late June the regiment was still in England with
100 AA Bde, waiting to be called for embarkation. As 100 AA Bde's units arrived in Normandy, they were at first placed under the command of
80 AA Bde, tasked with defending the eastern end of the beachhead. However, by July, the Luftwaffe was reduced to sporadic raids, and the HAA regiments, including 90th HAA, were frequently used to supplement the medium artillery in bombarding ground targets,
counter-battery (CB) fire, and anti-tank roles in the bitter fighting round
Caen. Once the city was captured, responsibility for its AA defence was handed over to 100 AA Bde. After 21st Army Group began to advance out of the beachhead in August, 100 AA Bde was able to pass responsibility for Caen over to
75 AA Bde and catch up with the advance. On 25 August, 100 AA Bde was protecting the
Seine crossings with 272 Bty of 90th HAA Rgt together with an LAA regiment, and by 4 September it was covering
XXX Corps' supply lines running from
Arras to
Antwerp with the whole of 90th HAA Rgt deployed, though the regimental transport vehicles had been taken to supply the advancing troops. XXX Corps made a further thrust in
Operation Market Garden, and 90th HAA Rgt was deployed to defend the crossings of the
Albert and
Meuse–
Escaut canals behind the start line. After the failure of Market Garden, 100 AA Bde's tasks were extended to include the captured bridges up to
Nijmegen and 90 HAA Rgt was brought up on 1 October (minus its Radar Troop, which was deployed elsewhere with LAA guns).
74 AA Brigade HQ took over responsibility for Nijmengen on 10 November, but 90th HAA Rgt remained in position. Protecting Nijmegen Bridge was the first 'proper' AA task the regiment had been given so far in the campaign: the guns were in action every night and occasionally during the day. 272 and 284 HAA Batteries also fired in the ground role in support of
43rd (Wessex) Infantry Division; 285 HAA Bty was precluded for this because its eight-gun AA battery position was under direct enemy observation. After six weeks the regiment moved south and deployed to provide AA defence for the communication centre of
Helmond, back under the command of 100 AA Bde. Little was seen of the
Luftwaffe in December 1944 and, towards the end of the month, 284 HAA Bty was lent to
8th Army Group Royal Artillery (AGRA) supporting
VIII Corps. It was deployed at
Overloon and
Boxmeer on the
River Maas in the ground role, primarily CB tasks. However, the regiment was busy in the AA role on 1 January 1945 when the
Luftwaffe launched
Operation Bodenplatte to support the
Ardennes Offensive. Hundreds of aircraft attacked Allied airfields. Most were fast-moving single-engined
Fighter-bombers, which were not good HAA targets, but two were brought down by the regiment's
Bren guns, one by 284 HAA Bty deployed in its medium artillery role, the other by 285 HAA Bty.
Rhine crossing On 1 March, 90th HAA Rgt came out of the line and moved to
Nieuwpoort, Belgium on the coast. XII Corps released 90th HAA Rgt from its AGRA tasks at 05.30 on 25 March: 272 HAA Bty then moved up into position on the west bank, while the other two batteries were held in readiness, and crossed the river that evening. These batteries deployed at once into eight-gun positions alongside LAA batteries to provide AA cover as the
Luftwaffe attempted to disrupt the bridging operations. The regiment engaged 14 enemy aircraft that night, of which nine adopted evasive action on their run-in. What appeared to be radar jamming turned out to be the sheer volume of AA and other shells visible on the screens. On the following night, the regiment engaged 17 aircraft and brought its total of 'kills' up to six. By 28 March, the bridges were all complete and 21st Army Group was beginning its drive across Germany. 90th HAA Regiment settled down with 100 AA Bde to defend XII Corps' bridges at
Xanten in a full-scale IAZ with HAA, LAA, searchlights and radar. Apart from some slight daytime activity by fighter-bombers, the
Luftwaffe now ceased operations along the Rhine. The AA tasks having disappeared, the AA brigades were put to other uses. 90th HAA Regiment was 'grounded' and its vehicles used for general transport for the advancing armies, while the gunners secured
Prisoners of War and captured material, removed roadblocks and carried out battlefield clearance. These tasks continued after the
German surrender at Lüneburg Heath as part of the occupation forces in Germany while awaiting
demobilisation. 90th HAA Regiment was placed in suspended animation in
British Army of the Rhine on 1 March 1946. ==Postwar==