At this stage of the war 40 AA Bde operated as a 'light' AA brigade composed of S/L and LAA units, but in July a section of 286 HAA Bty from 91 HAA Rgt in the Humber Gun Zone was sent to the brigade to man two semi-mobile 3-inch guns to defend RAF Horsham St Faith under 29th LAA Rgt.

[21] As more LAA units became available, they were distributed to defend Vulnerable Points (VPs) such as airfields, which were attacked during the Battle of Britain.

The cluster system was an attempt to improve the chances of picking up enemy bombers and keeping them illuminated for engagement by AA guns or RAF Night fighters.

By this stage of the war AA Command was being forced to make manpower cuts, releasing men to 21st Army Group for Operation Overlord, the planned Allied invasion of Normandy, and a number of S/L btys were disbanded: 72nd and 82nd S/L Rgts each lost one.

[50][52][53] 5 AA Group was now acting as a reserve: some units and formations left to join Overlord after D-Day in June, and when the long-awaited attacks on London by V-1 flying bombs ('Divers') began shortly afterwards), AA Command put into action its planned countermeasures (Operation Diver).

[56] The first phase of V-1 attacks ended in September 1944 after 21st Army Group overran the launching sites in Northern France.

In October, AA Command began planning to counter the expected attacks by air-launched V-1s coming in across the North Sea against targets on the East Coast and the Midlands.

The brigade was reduced to a single regiment (172nd (M) HAA Rgt), but was tasked with reconnoitring and establishing 10 new AA gun sites from Donna Nook to Wainfleet along the Lincolnshire coast.

The guns were emplaced on temporary 'Pile platforms' named after the Commander-in-Chief of AA Command, Gen Sir Frederick 'Tim' Pile.

However, on 24 December the Luftwaffe began launching the missiles across the Lincolnshire coast aimed at Manchester, and the Diver Fringe was activated with HAA and LAA batteries moving into 41 AA Bde's area.

[53][60] The composition of the brigade during the period was as follows:[53] As the war in Europe drew to its end in early 1945, demobilisation of AA Command proceeded rapidly as manpower was diverted to other roles.