[2][3] Coming directly under General Headquarters (GHQ) the brigade's role was to administer the S/L units deployed to protect airfields, ports, and the BEF's forward gun areas.

On 17 May it detached a group of riflemen with Boys rifles to defend 5 AA Bde HQ at Lens while the remainder joined the Bethune canal guards.

They were joined on 22 May by 30th Infantry Brigade, just before advanced German troops began probing the defences, beginning the Siege of Calais.

But ground attack was now the biggest danger, and the S/L men had to man the perimeter as infantry, a role for which they (mainly older Territorials, raw militiamen and a few ex-RE reservists) were untrained.

While part went to Calais, a Troop of one officer and 80 men found themselves attached to K Battery, Royal Horse Artillery, with orders to help hold the small village of Hondeghem which was on the main German axis of advance.

The gunners fought a valiant action on 26 May then, running short of ammunition, they charged the German positions and broke through, giving them a route out towards Dunkirk.

The Gloster Aircraft Company factory at Brockworth, Gloucestershire, was a strategic target in the area and was protected by 24 HAA guns.

[27][28] By about 18 July the reformed HQ had taken over the following units:[27] In November 1940, as the Luftwaffe's night bombing campaign against British cities (The Blitz) was getting under way, there was a major reorganisation of AA Command.

Otherwise, enemy air activity was reported as 'slight' and 'small scale', and was mainly heading towards Birmingham and Coventry in the neighbouring 11 AA Division area, with one raid on Cheltenham on 11 December.

[40][41][42] From November 1940 searchlights were deployed in clusters of three lights in an attempt to improve the chances of picking up enemy bombers and keeping them illuminated for engagement by AA guns or Royal Air Force (RAF) night-fighters.

The number of LAA units to protect Vital Points (VPs) such as aircraft factories and airfields was growing, albeit slowly.

[39][62][63] The turnover of units accelerated with the need to provide AA cover for the Allied invasion of North Africa (Operation Torch) in late 1942 followed by the landings in Sicily and Italy in 1943.

Meanwhile, the Group also had to deal with a sharp increase in Luftwaffe air raids trying to reach London during the winter of 1943–4 (the so-called 'Little Blitz').

[39][83][84] During this period 5 AA Bde's composition was as follows:[82][84] The first V-1 missiles were fired against London in June, a week after D-Day, and Operation Diver was activated.

Firstly, mobile HAA guns were replaced with static installations that could traverse more quickly to track the fast-moving targets.

The whole process involved the movement of hundreds of guns and vehicles and thousands of servicemen and women, but a new 8-gun site could be established in 48 hours.

The guns were constantly in action, but the success rate against the 'Divers' steadily improved, until over 50 per cent of incoming missiles were destroyed by gunfire or fighter aircraft.

This phase of Operation Diver ended in September after the V-1 launch sites in Northern France had been overrun by 21st Army Group.

AA Command had to reorganise its defences, stripping HAA guns from inland sites and moving them to the coast of East Anglia, together with Pile platforms and accommodation huts.

[90] At the same time the Luftwaffe was suffering from such shortages of pilots, aircraft and fuel that serious aerial attacks on the United Kingdom could be discounted.