1 AA Group was formed on 1 October 1942 when
Lieutenant-General Sir Frederick 'Tim' Pile, Commander-in-Chief of Anti-Aircraft Command (AA Command), scrapped its previous conventional structure of
Corps and
Divisions. Each of the new AA Groups was commanded by a
major-general and controlled a number of
AA Brigades and support units. The new group boundaries were aligned with the Fighter Groups of the
Royal Air Force (RAF). (It was jokingly observed that a reorganisation that eliminated eight general officers was the best contribution to the war effort at the time!) The first
General Officer Commanding (GOC) of 1 AA Group was Maj-Gen
Erroll Tremlett, who had previously commanded
10 AA Division. A former
first-class cricketer, Tremlett had distinguished himself earlier in the war when he commanded
54th (Argyll and Sutherland Highlanders) Light Anti-Aircraft Regiment, Royal Artillery defending the mole during the
Dunkirk evacuation. closed in 1934, used as the headquarters of the London Inner Artillery Zone AA defences during World War II.
Order of Battle 1943–44 When they were first established there was much interchange of the units allocated to 1 and 2 AA Groups, but from early 1943 1 AA Group had the following order of battle (temporary attachments omitted): •
26 (London) AA Brigade • 111 Heavy AA (HAA) Regiment, Royal Artillery (RA) –
to 21st Army Group by August 1943 •
132 (Mixed) HAA Regiment, RA –
to 2 AA Gp July 1944 •
137 (Mixed) HAA Regiment, RA • 156 (Mixed) HAA Regiment, RA •
48 AA Brigade •
117 HAA Regiment, RA –
from Orkney and Shetland Defences (OSDEF) October 1943; to 2 AA Gp May 1944 • 141 (Mixed) HAA Regiment, RA –
to 7 AA Gp December 1943 •
155 (Mixed) HAA Regiment, RA • 160 (Mixed) HAA Regiment, RA –
from 2 AA Gp by March 1944 •
163 (Mixed) HAA Regiment, RA • 164 (Mixed) HAA Regiment, RA –
left October 1943 •
49 AA Brigade • 141 Light AA (LAA) Regiment, RA –
to Gibraltar August 1943 •
26 (London Electrical Engineers) (Mixed) Searchlight (S/L) Regiment, RA •
80 S/L Regiment, RA –
from 4 AA Gp by April 1944 • 1 (Mixed) AA 'Z' Regiment, RA • 6 AA 'Z' Regiment, RA –
to 37 AA Bde August 1943 • 14 AA 'Z' Regiment, RA –
to 4 AA Gp April 1943 • 19 (Mixed) AA 'Z' Regiment, RA • 301 Gun Operations Room (GOR),
Stanmore • 601 GOR,
Brompton Road • 1 AA Group School,
Chelmsford • 1 AA Group (Mixed) Practice Camp •
1 AA Group Mixed Signal Unit,
Royal Corps of Signals (RCS),
Uxbridge • 1 Mixed Signal Company • 1 AA Command Mixed Signal Office Section (under AA Command) • 1 AA Group Mixed Signal Office Section • 26 AA Bde Mixed Signal Office Section • 48 AA Bde Mixed Signal Office Section • 49 AA Bde Mixed Signal Office Section • 4 AA Line Maintenance Section • 2 Mixed Signal Company • 301 GOR Mixed Signal Section • 601 GOR Mixed Signal Section • 5 AA Line Maintenance Section • HQ 1 AA Group
Royal Army Service Corps (RASC) • 900, 902, 907 AA (M) Transport Companies • 919, 921 AA (M) Transport Companies –
joined November 1943 • 1 AA Group
Royal Army Medical Corps (RAMC) Company • 1 AA Group
Royal Army Ordnance Corps (RAOC) • 10 AA Workshop Battalion,
Royal Electrical and Mechanical Engineers (REME) • 1, 6 AA Workshop Companies • 1 AA Group Radio Maintenance Company –
later divided into 101 and 102 Radio Maintenance Detachments; joined by 105 Detachment June 1944 'Mixed' indicates that women of the
Auxiliary Territorial Service (ATS) were integrated into the unit. HAA regiments were equipped with
3.7-inch guns, LAA regiments with
Bofors 40 mm guns, 'Z' Regiments with
Z Battery rocket projectors, and S/L regiments with a variety of searchlights and
Light machine guns. By August 1943 the Group had taken over control of two further AA brigades, with the associated signal units: • 328 GOR,
Fort Luton •
37 AA Bde –'' 'Thames North' '' • 121 HAA Regiment –
to 21st Army Group by September 1943 However, in January 1944 it resumed night raids on London, which became known as the '
Baby Blitz'. These raids employed new faster bombers with sophisticated 'pathfinder' techniques and radar jamming. For example, on the night of 21 January 200 hostile aircraft were plotted approaching the South Coast in two waves, which intermingled with returning aircraft of
RAF Bomber Command. This caused problems of identification and restrictions on fire, but the guns of 2 AA Group and then 1 AA Group engaged as the raiders approached London. Only one-fifth of the raiders reached the city, the remainder turning away to bomb open country. AA guns brought down eight aircraft and RAF
Night fighters with S/L assistance also had successes. At the end of January London Docks received a 130-strong raid dropping flares and incendiaries as they had in the
London Blitz of 1940–41: about one-third reached their target and five were shot down. February began with a 75-strong raid, of which only 12 reached the IAZ and four were shot down. On 13 February only six out of 115 bombers reached London. The climax came with five raids in the week 18–25 February varying from 100 to 140 in strength. These met intense AA fire from the Thames Estuary onwards and fewer than half made it to
central London: the AA score was 13 shot down while the night fighters and S/Ls added 15, with another shared. Facing these casualty rates, the
Luftwaffe switched to targets away from London until 24 March, when a 100-strong raid on London lost four aircraft, and finally on 18 April a raid of 125 aircraft lost 14 shot down and only 30 reached the IAZ. Although much damage was caused in London, the rising efficiency of the HAA guns and radar made the enemy's losses unsustainable. By February 1944, 1 AA Gp was responsible for the AA Operations Room at Brompton Road and the following GORs: At the end of June Pile ordered a change in AA Command's tactics: instead of deploying mobile 3.7-inch guns in the Diver Belt, the most up-to-date power-controlled static guns, radars and predictors would be used, which involved a massive redeployment of guns uprooted from all over Britain and emplaced on temporary 'Pile Platforms'. The task was made bigger by the decision to move the Diver Belts to the coast itself, giving the guns a free fire zone out to sea. On 16 July 1 AA Group was ordered to form a 'Diver Box' of gun defences across the Thames Estuary, forward of a line from Chelmsford in
Essex to
Chatham, Kent. The removal of so many guns, and the silencing of those remaining in the IAZ, led Londoners to believe that the city was being defended by the RAF alone. As 21st Army Group began to overrun the V-1 launching sites in Northern France, the
Luftwaffe turned to launching the missiles from aircraft over the
North Sea, and 1 AA Group's Diver Box was heavily engaged. It was equipped with 136 Mark IIC 3.7-inch guns with No 10 Predictors and
SCR-584 radar (some manned by three US Army AA Artillery battalions), 210 Bofors guns, and two Z Batteries of mobile nine-rocket launchers manned by a converted S/L regiment. The HAA guns began using the proximity
VT fuze with great success. A number of the guns were mounted on the
Maunsell Forts in the Thames Estuary. In addition there were 400 20mm guns provided by the
RAF Regiment and the
Royal Navy. To control these guns the Box was divided into four sectors under 37, 49, 56 and 68 AA Brigades. H-22 carrying a V-1 flying bomb. Success rates for AA Command began to rise during this second Diver deployment: from a 9 per cent success rate in July, the average rose to over 50 per cent. On one day 68 missiles were destroyed out of 96 plotted. The weekly total of missiles reaching London fell from a peak of 362 in July to 100, then down to 10 in September. A further redeployment of guns from the South Coast through London to the East Coast was ordered on 21 September. 3 AA Group HQ was brought from
Bristol to take over command of the London IAZ, and a new 9 AA Group took over
East Anglia, leaving 1 AA Group to concentrate on the Diver Box and the Thames/
Medway and
Dover defences (though this was still a massive command temporarily controlling 10 AA brigades). The second phase of V-1 attacks ended in mid-January 1945. AA Command's success rate in this phase was impressive: out of a total of 492 V-1 targets, 320 were shot down, and only 13 reached London.
Order of Battle late 1944 From mid-October 1944, 1 AA Group had the following order of battle: Maj-Gen Tremlett was replaced by Maj-Gen Roger Reynolds on 1 November 1944.
Order of Battle 1945 From mid-December, when the worst of the V-1 threat to London had receded and AA Command was being forced to supply manpower to 21st Army Group fighting in NW Europe, 1 AA Group had the following reduced order of battle: ==Cold War==