[4][5][6] At the time the brigade was formed, the TA's AA units were in a state of mobilisation because of the Munich crisis, although they were soon stood down.

Attacks on Royal Navy bases early in the so-called Phoney War period prompted calls for stronger AA defences at Scapa Flow, Invergordon, Rosyth and the Clyde anchorage, and 3rd AA Division was given priority for delivery of HAA guns.

A new Luftwaffe attack on 16 March 1940 caught the defences half-prepared: only 52 out of 64 HAA guns were fit for action, and 30 out of 108 searchlights.

About 15 Junkers Ju 88s approached at low level in the dusk: half dived on the warships and the rest attacked the airfield.

44 HAA guns of 42 AA Bde engaged, but their predictors were defeated by erratic courses and low height.

[15][17] The industrial town of Clydebank near Glasgow was badly hit on the nights of 13/14 and 14/15 March 1941 in the 'Clydebank Blitz', but none of the raiders was brought down by AA fire.

[12][31][28] The composition of the brigade was completely reorganised in the summer of 1941, giving it the following order of battle from September (temporary attachments omitted):[26][34][35] The AA divisions in the UK were disbanded in September 1942 and replaced by a system of AA Groups corresponding to the Groups of RAF Fighter Command.

[38][39] The composition of the brigade at this time was as follows (temporary attachments omitted):[40][41][42] By early 1944 aerial attacks against Scotland were rare and the AA defences could be scaled back.