In September 1939, the British Army was in process of expanding their anti-aircraft and mobile (including armoured) assets.
Aldershot Command's geographical area encompassed portions of the following counties Berkshire, Hampshire, Surrey, Sussex.
Its primary formations on the outbreak of the war were:[1] Northumbrian Area, Darlington: comprising the counties of Northumberland, County Durham, North Riding of Yorkshire (excluding Catterick Area and Strensall Camp), East Riding of Yorkshire; also Berwick-upon-Tweed (except regulars).
Highland Area, Perth: covering the counties of Sutherland, Caithness, Ross and Cromarty, Inverness-shire, Nairnshire, Morayshire, Banffshire, Aberdeenshire, Kincardineshire, Angus, Perthshire, Kinross-shire, Fife, Clackmannanshire, Stirlingshire, Dumbartonshire, Renfrewshire, Buteshire, and Argyllshire.
Lowland Area, Darlington: comprising the counties of West Lothian, Midlothian, East Lothian, Berwickshire (including Berwick-upon-Tweed for Regulars and Militia only), Roxburghshire, Dumfriesshire, Kirkcudbrightshire, Wigtownshire, Ayrshire, Lanarkshire, Peeblesshire, Selkirkshire; and (for Clyde and Forth Defences only), and Fife.
Eastern Command was one of two southern commands, itself overseeing the areas of: Cambridgeshire, Norfolk, Suffolk, Essex (except Purfleet and Rainham rifle ranges; and (when occupied by Foot Guards) the Guards' barracks at Warley Barracks), Hertfordshire, Bedfordshire, Middlesex, Kent, Sussex, and Surrey (less portion in the Aldershot Command and London District), and Woolwich Garrison (exclusive of the Territorial Army troops quartered there).
East Anglian Area covered the counties of Cambridgeshire, Norfolk, Suffolk, Essex, Middlesex, Hertfordshire, and Bedfordshire (less the following: Colchester Garrison, Purfleet Rifle Range, and Rainham rifle ranges (when occupied by the Foot Guards) the Guards' Barracks at Warley Barracks which area under London District, That partition of Essex in Chatham Area from Grays Thurrock Station along main road to Stanford-le-Hope, thence north side of railway via South Benfleet to Southend-on-Sea borough boundary - thence a line drawn north-east to Lower Edward's Hall - thence road eastwords to Harp House - thence a line south-east to Southchurch Lawn - thence a line due north to River Roach - thence along south bank of River Roach and south bank of River Crouch to Foulness Point).
Chatham Area covered the areas of: Foulness Point (Essex) by a line drawn south to Shellness (Kent) thence a line drawn south-west to Ladydane thence along a road to Watling Street thence Watling Street to road Faversham, Leaveland, Challock Lees, Chaning, Lenham, Harrietsham, Elsfield, Hollingbourne thence Pilgrim's Way via Detling, Burham, Snodland thence via Pilgrim's Road to Trosley Towers thence along road Wrotham-Gravesent to Northumberland Bottom thence Watling Street to Southern Railway Bridge at Springhead thence northward along stream to River Thames, along south bank of River Thames to lighthouse on Swanscombe Marshes thence by a line drawn northeast across the River Thames to Grays Thurrock Station (Essex) thence along the main road to Stanford-le-Hope thence northside of railway via South Benfleet to Southend Borough boundary thence a line drawn northeast to lower Edward's Hull thence along road Eastwood to Harp House thence a line drawn south-east to Southchurch Lawn thence a line due north to River Roach, along south bank of River Roach and south bank of River Crouch to Foulness Point.
South Midland Area comprising: Counties of Warwickshire, Northamptonshire, Huntingdonshire, Buckinghamshire, Berkshire (except Victoria Barracks and Combermere Barracks and portions in Aldershot Command), Oxfordshire, Gloucestershire (except Beachley), Worcestershire, and Wiltshire north of the Salisbury Plain Area.
5th AA Division covering Bristol, Plymouth, Portsmouth, Isle of Portland, Southampton, and Cardiff.
Middle East Command controlled all the forces based in: Sudan, Aden, Somaliland, Palestine, Transjordan, and Egypt.
The Pacific Ocean region comprised the areas of: Fiji, Sarawak, and the Gilbert and Ellice Islands Colony.
The Royal West African Frontier Force or also known as the West African Force comprised troops from the areas of Colony of Nigeria, Gold Coast Protectorate, Colony of Sierra Leone, Gambia Protectorate, and the Cameroons Mandate.