98th Heavy Anti-Aircraft Regiment, Royal Artillery, was an air defence unit of Britain's Territorial Army (TA) formed in Gloucestershire during the period of international tension leading up to the outbreak of World War II.

A detachment from 301 HAA Bty took up defence of the Bristol Aeroplane Company factory at RAF Filton on 31 August, equipped with 12 Lewis guns in case of low-level air attack.

[2][8] At the beginning of October RHQ moved from Cheltenham to Rudgeway and a month later it took over operational control of 439 Bty, 63rd (4th Bn Queen's) Searchlight Rgt, which had 24 Lewis gun teams deployed at Avonmouth Docks.

During March drafts of men were received from the training regiments, together with a group of junior officers transferred from 54th (City of London) HAA Rgt.

Ten days later the battery was moved to Weybridge to protect the Vickers and Hawker aircraft works at Brooklands under 47 AA Bde, manning eight mobile 3.7-inch guns.

RHQ moved from Rudgeway to the Militia Camp at Fernhurst in West Sussex, which was closer to these units:[2] While the Battle of Britain raged over South East England in August and September, the regiment was progressively concentrated round Weybridge:[2] At the beginning of September the Luftwaffe shifted its attention away from RAF Fighter Command's airfields and radar stations and began attacking targets nearer London.

[12][15][16] The Royal Artillery's historian considered that during these attacks on British cities 'the actions fought [by the AA batteries] were as violent, dangerous and prolonged as any in the field'.

By now the HAA sites had the advantage of GL Mk I* radar with an elevation finding (E/F or 'Effie') attachment to supplement searchlights, and some of the gunsites replaced 3.7-inch with 4.5-inch guns.

[2][18][21][16][22][23] 399 HAA Battery was reinforced by 25 other ranks transferred from the Royal Welch Fusiliers on 25 June and three days later established a new C Site at Audenshaw with four mobile 3.7-inch guns.

[18][24] In January 1942 the regiment received a number of AEC Matador gun tractors and drivers, which led to rumours that it was to mobilise for service, which were soon confirmed.

[26] On 29 April the regiment moved south, towing its mobile 3.7-inch guns, which were deployed to defend Andover, Salisbury and Winchester, with RHQ at Nether Wallop in Hampshire.

In December it was joined by its signal section of the Royal Corps of Signals (RCS) and workshop section of the Royal Electrical and Mechanical Engineers (REME), giving it the following organisation:[25][29][30] In January 1943, the whole regiment moved to Coupar Angus in Scotland, from where it spent two weeks in February at 2nd HAA Training and Practice Camp at Burrow Head.

The regiment was relieved on 24 August and moved to Norwich and Lincoln to take over sites from 197th HAA Rgt, then returned to its old location at Carburton Camp by 10 September.

[d] After another exercise in the Whitby area, the regiment moved at the end of the year to Southend-on-Sea under 75 AA Bde, another 21st Army Group formation.

[25] 75 AA Brigade and its units were follow-up forces for Operation Overlord, and remained in the UK after D Day, not crossing to Normandy until 21st Army Group broke out of its constricted beachhead in late August.

[32] After landing on 29 August the brigade took over AA defence of Caen, releasing the units there to join Second Army's pursuit of the defeated Germans after the Battle of Falaise.

Given the lack of Luftwaffe activity the AA allocation to Ostend was too generous, and on 31 October the regiment moved to Tirlemont, south-east of Brussels.

[34][35] Once 21st Army Group captured Brussels and Antwerp, these cities had become targets for V-1 flying bombs (codenamed 'Divers') launched from within Germany, and anti-Diver or 'X' defences had to be established.

AA Command's experience against V-1s launched at England during the summer had shown that the power-operated, remotely controlled Mk IIC 3.7-inch gun, with automatic fuze-setting, SCR-584 radar and Predictor No 10 (the all-electric Bell Labs AAA Computer) were required to deal effectively with V-1s, but 21st Army Group's mobile HAA units did not have experience with this equipment and were at a disadvantage.

As more static guns arrived, part of 98th HAA Rgt moved on 19 November to the area of Goes in South Beveland where the Battle of Walcheren had just ended.

Despite concerted attacks on nearby airfields by Luftwaffe fighters on 1 January (Operation Bodenplatte), the ground situation was well under control and the AGRA and local defence plans were cancelled on that day.

On 21 January the whole regiment was ordered to concentrate on South Beveland, where the batteries already in position provided bridges, huts and bivouacs for the main body moving in from Tirlemont.

98th HAA Regiment formed a gun tractor platoon on 15 March to assist the Royal Engineers in moving equipment of the Rhine crossing (Operation Plunder).