As the British Expeditionary Force (BEF) in France expanded during the Phoney War period of early1940, new headquarters (HQs) were formed to control the various groups of anti-aircraft (AA) guns and searchlights (S/Ls) that were deployed to defend its field formations and base installations.

Since then it had moved between AA brigades and had suffered a constant turnover of batteries exchanged with other regiments, leading to complaints from the commanding officer (CO).

Coming directly under General Headquarters (GHQ) the brigade's role was to protect supply points and airfields behind the BEF's frontline forces.

[8][9][10] During the Battle of France the brigade had the following composition:[8][3][11][12] Following the German invasion of the Low Countries the BEF followed the pre-arranged Plan D and advanced into Belgium to take up defences along the Dyle.

Forced to retire towards Dunkirk, the BEF's AA brigades were sucked into the ground battles, split into sub-units in rearguard actions, or moved back to cover successive key points.

The Gun-Laying (GL) radar sets were sent back, and I Corps employed the regiment's batteries on bridges and routes to cover its withdrawal against high level and dive-bombing attacks.

The next six days saw alternate moves and deployments in small units of Troop and Section size at Armentières, Hazebrouck, Poperinghe and other places under shellfire and Stuka attack.

When the supply chain failed, a search party found a stock of ammunition on a loaded train in a railway siding.

[13][14] By 26 May the decision had been made to evacuate the BEF from Dunkirk (Operation Dynamo), with I Corps controlling the rearguard including 4 AA Bde.

1 LAA Bty moved up as separate Troops attached to columns of 7th Armoured Division, covering 150 miles (240 km) of rough going in 30 hours.

There was virtually no enemy air activity as the Italian Tenth Army collapsed, with many thousands surrendering, but within a few days aircraft of the Regia Aeronautica joined by the Luftwaffe began bombing the British forward supply point that had been established at Benghazi.

The regimental historian notes that these Stuka attacks concentrated on gun positions, which was a serious threat to HAA sites, whose instruments could not cope with the rapid height changes.

The gunners devised a tactic of opening fire with short Fuzes just before the dive started, to force the pilots to fly through a ring of bursts.

Aircraft attempting to lay parachute mines in the approaches were usually driven off by a low-level concentration of all available guns into a searchlight-illuminated target area.

In the last two months of the siege, troops of HAA guns took it in turn to move out to the perimeter and take on ground targets under the control of 9th Australian Division.

[35] In November 1941 the British Eighth Army began a new offensive in the Western Desert (Operation Crusader), which succeeded in ending the Siege of Tobruk.

[46] During the Battle of Gazala, beginning on 26 May, Rommel's Axis forces quickly broke into the British position and began attacking the defensive 'boxes'.

The British hoped to defend Tobruk as in the previous siege, but this time the Axis forces reached it before the defences were ready.

The gunners stripped down the walls of their emplacements to permit low-angle fire and engaged the tanks with armour-piercing and high explosive rounds.

[50][51] After the fall of Tobruk, the Eighth Army retreated in confusion beyond the Egyptian frontier until the Axis advance was finally halted at El Alamein.

At first it had the following order of battle:[54][55] However, the latter two regiments were soon sent forward as divisional troops and Wilson's planned AA defences never reached their full extent.

After the German defeat at the Battle of Stalingrad the Luftwaffe was never in a position to attack Iraq or Persia and from April 1943 the AA defences were run down.

4 AA Brigade concentrated on defending RAF Habbaniya, Basra and a few oilfields, but it was given two important training tasks in addition to its operational commitments.