Increasing concern during the 1930s about the threat of air attack led to large numbers of units of the part-time Territorial Army (TA) being converted to anti-aircraft (AA) gun and searchlight roles in the Royal Artillery (RA) and Royal Engineers (RE), and higher formations became necessary to control them.

[5][6] The divisional badge was a falling black aircraft silhouette trailing red flames, on a khaki background.

[18] After these preliminary skirmishes, the battle intensified from 13 August with bombing raids primarily directed against Fighter Command's airfields.

Some of the greatest battles were fought on 15 August, from South Wales to the Yorkshire Coast, when the 5th AA Division was hotly engaged.

On that day Lehrgeschwader 1 (LG 1) made a heavy raid of 70–80 bombers escorted by single- and twin-engined fighters against the South Coast.

(St)/LG 1 and escorting Bf 110 Zerstörers of V.(Z)/LG 1 heading for RNAS Worthy Down were attacked out of the sun, dropped a few bombs at Portland and withdrew with heavy losses.

(St)/LG 1) flew on to attack RAF Middle Wallop, causing some damage, but suffering further casualties.

Between the fighters and the AA guns at Portsmouth and Southampton, the Geschwader lost 8 bombers, 4 Stukas and 13 Bf 110s, as well as many others damaged.

[21] The climax of the battle was on 15 September, when massed raids attacked London and suffered severe casualties from the fighters and guns.

[22] After its crushing losses in day raids, the Luftwaffe switched to night bombing of London and the industrial cities ('The Blitz'), with Southampton, Cardiff and Swansea being among the targets attacked using Knickebein navigation aids.

[23] During the Portsmouth Blitz, two bombs dropped directly on a position of the 35th AA Brigade, killing an officer and 10 men, wrecking the command post and one gun.

A new Luftwaffe campaign against the mainland UK opened in March 1942, with a series of low-level fighter-bomber attacks against coastal towns, many in the 5th AA Division's area, which had few LAA guns available for defence.