The 90th Light Anti-Aircraft Regiment, Royal Artillery, (90th LAA Rgt) was an air defence unit of the British Army during World War II.

The unit was originally formed in May 1940 as 50th Holding Battalion, South Wales Borderers, as part of the rapid expansion of the Army with wartime conscripts.

From 19 February 1941 the brigade was temporarily attached to 59th (Staffordshire) Infantry Division, at that time serving in X Corps in the invasion-threatened south-east corner of Kent.

In the rough country of Tunisia the forward LAA units were often involved in 'snap' engagements against fast, low-flying air attacks.

[14] On 23 April 1st Division launched its attack against a line of low hills, with considerable artillery support, but found the captured ground too hard to dig in, and was thrown back by counter-attacks.

That evening it took Djebel Bou Aoukaz with massive artillery support, securing the flank for First Army's main attack early next morning.

Pantelleria was rumoured to be an island fortress, but after massive air and naval bombardment, the garrison surrendered without any land fighting.

There were some subsequent air attacks from Sicily, but a number of British AA units had been landed with radar to defend the captured island, and 1st Division was soon back in North Africa.

The Germans quickly contained the beachhead and by 1 February were attempting to drive the Allied troops back towards the sea, and sending over waves of air attacks.

By 19 February Turner was reinforced by the other two batteries of 100th LAA Rgt to extend the fire plan, one of which was stationed aboard Landing Ship, Tank, vessels moored in Anzio harbour.

Raids continued all through March, in strengths varying from single aircraft to 20-plus, while the grim fighting along the front often drew in the LAA troops to give fire support to the infantry.

Although the tempo of air attacks declined in April, the calls for support from the infantry engaged in Trench warfare were endless.

On 21 April alone, 90th LAA Rgt fired 3425 rounds against German infantry working their way up dry river beds into the Allied positions.

90th LAA Regiment receives special praise from the Royal Artillery historian for remaining in action from the first day to the last of the Anzio campaign.

However, by mid-October the offensive had begun to lose impetus in the Apennine Mountains as the Allied supply lines were stretched and the difficulty of finding suitable gun positions increased.

As early as June 1944 the Chiefs of Staff had decided that the number of AA regiments in Italy must be reduced and their fit personnel converted to other roles, particularly infantry.