The 40th Light Anti-Aircraft Regiment, Royal Artillery, (40th LAA Rgt) was a Scottish air defence unit of Britain's Territorial Army (TA) during World War II.

It landed in Normandy on D + 1 and fought through the campaign in North West Europe, including the crossing of the Rhine, until VE Day.

The regiment was formed as part of the rapid expansion of Britain's anti-aircraft (AA) defences at the beginning of World War II.

Instead of being deployed in circles round objectives, the LAA guns were sited on the attackers' likely lines of approach, where opening fire would not give away the presence of a likely target, and numerous dummy and alternatives positions were prepared.

When the initial artillery bombardment began on the night of 23 October, LAA batteries switched from defending the assembly areas to firing Tracer ammunition to mark the attacking units' boundaries in the dust and darkness.

[21] The division remained outside the city while Eighth Army probed forward to Tunisia; 40th LAA Rgt with 35 Bofors was loaned to 2 AA Bde in Tripoli for XXX Corps defence tasks.

In the rough country of Tunisia, LAA units were often engaged in 'snap' actions against fast low-flying aircraft, usually coming out of the sun.

Once ashore the divisional LAA regiments were assigned to beach defence, though they were hampered by the lack of a workable early-warning system.

LAA batteries were reduced to firing prepared concentrations, either directional ('Curtains') or overhead ('Umbrellas'), which were ineffective and wasted scarce ammunition.

However, resistance had stiffened, the division was unable to cross the River Simeto, and it had to fight hard to capture Gerbini Airfield.

[26][27] After Eighth Army had regrouped, 51st HD was employed in a thrust towards Adrano at the foot of Mount Etna, beginning with a crossing of the River Dittaino on the night of 31 July/1 August.

[28][29] 51st (H) Division was among the formations selected to be withdrawn from the Mediterranean Theatre to return with XXX Corps to the UK to train for the Allied invasion of Normandy (Operation Overlord).

LAA units fired tracer to guide night attacks onto their objectives, and the Bofors guns were much in demand for infantry support.

LAA units also provided 'refuge strips' for air observation post aircraft spotting for the field guns: a Bofors troop deployed with local warning radar and ground observers could alert the pilot to the presence of enemy aircraft and provide protection for him.

[37] After a long period fighting in the Bocage country, Operation Totalize carried out by II Canadian Corps (including 51st HD) on the night of 7/8 August attempted to complete the breakthrough.

[40][41][42][43] The division next made a long move to the Antwerp area at the end of September, then spent three weeks in the line at Sint-Oedenrode.

[48][49] In December the division was suddenly moved south as part of the response to the German breakthrough in the Ardennes (the Battle of the Bulge), and 51st HD fought its way into the flank of the 'Bulge' in winter conditions.

[50][51] When the Luftwaffe launched its Operation Bodenplatte against Allied airfields on 1 January 1945, GHQ AA Troops for 21st Army Group reported that '40 mm LAA had the time of its life' shooting down large numbers of raiders.

The corps launched its attack at 05.00 on 8 February, and as the field and medium artillery concentrated on the enemy's batteries, command posts and communication centres, the divisional LAA regiments took part in the 'Pepperpot', in which guns and mortars of all calibres saturated the enemy positions in front of the assaulting infantry.

51st (H) Division was tasked with making the initial assault crossing on XXX Corps' front (Operation Turnscrew).

When the operation was launched on the night of 23/24 March, 40th LAA Rgt took part in the corps 'Pepperpot', its Bofors firing 11 serials, each lasting two minutes, in bursts of 10 rounds at 'automatic'.

It also fired low-angle tracer lines to guide the amphibious Buffaloes crossing the river in darkness, and then engaged ground targets in support of the assault.

It was not until after dark on 24 March that small numbers of Luftwaffe aircraft appeared, making dive-bombing attacks from medium and low altitude, which were countered by searchlights and LAA guns.

For the divisional LAA guns most of these involved 'snap' actions, against low-flying attackers using cloud cover, and often using jet aircraft.

The number of Luftwaffe attacks on the advancing divisions peaked in the last week of the war before the German surrender at Lüneburg Heath came on 4 May.