Throughout 1915 there was no major reassessment of the risk of invasion. However preparations for invasion were stepped up following enemy naval raids and the realisation that the War was not going to be over any time soon. During the summer of 1915, battalions for Home Service formed from Territorials unfit for overseas service or who had not volunteered for overseas service were raised, known as Provisional Battalions. These were entrenched along the East and South-east Coasts and were the first line of defence against invasion. The intention was now to meet the enemy on the coast and either defeat any invasion attempt or pin down the enemy on the beaches until reinforcements could arrive. The Yeomanry and Cyclist battalions were to reinforce the Provisional battalions as soon as the section of the coast on which the invasion was to be made became clear.
Right: Home Defence Troops, Suffolk Nov 1915
Arrangements were made to reinforce Scottish and Northern Commands (Emergency Scheme (A)) and Central Force on the east coast of England (Emergency Scheme (B)) with troops in stationed at Aldershot or Salisbury Plain by rail. Due to the time taken to entrain and the limitations governing rail transport, it was envisaged that not more than two divisions would be employed in the first instance. Complete units and formations were to be kept together as far as possible. Troops were to move within 12 hours notice (if two divisions were to be sent, the second division was to be ready to move within 18 hours).The General Officer Commanding the Command to be reinforced would select the stations for detrainment. To enable this certain stations on the route were designated “regulating stations”, which each train would pass through where they would be directed to the designated detraining station. Extra guards were to be detailed along the rail routes used for these movements.
Troops were to take three days rations and ammunition if they were in possession of their equipment ammunition. If this was not possible, ammunition would be drawn form the emergency stocks held at Aldershot and Salisbury Plain (where stocks of 12,000,000 rounds of small arms ammunition and 26,000 rounds of 18 pdr ammunition were eventually established). One station in the detraining area was to be designated an ammunition station to which all supplies of ammunition would be sent. Casualty Clearing stations were to be mobilized for each division from Aldershot Training Centre. Motor ambulances were to be dispatched by road to the regulating stations where they would receive orders for their final destination.
The London Defence Positions were constructed more or less as laid out in the pre-war plans to check any enemy breakthrough of the coastal defences. The work was carried out under the supervision of Major-General R.M. Ruck, General Officer Commanding London Defences. Should the situation necessitate, the London Defence Positions were to be manned by Special Infantry Brigades and a Reserve Artillery Brigade (Emergency Scheme (D)).
Above: Construction of the London Defence Positions
Emergency scheme (A) - Reinforcement of Scottish and Northern Commands
North of the Wash it was calculated that not more than 20,000 men could be landed before the Navy put an end to such an operation. Scottish and Northern Command had about 5,600 and 26,000 men respectively to meet such an attack. An Emergency Scheme was in place to reinforce these Commands with troops from Aldershot and Salisbury Plain by moving troops by rail. Detraining areas were as follows:
Area A – Stirling, Falkirk, Larbert
Area B – Edinburgh, Leith
Area B1 – Stow, Innerleithen, Galashields, St. Boswells
Area C – Newcastle and to the north
Area D – Newcastle and to the south
Area E – York, Salby and Doncaster
Area F – Doncaster, Bawtry, Worksop, Rotherham
A number of regulating stations were provisionally designated.
A flight of aeroplanes would also be sent to the Command being reinforced. Landing grounds were:
Scotland – Edinburgh (Redford Barracks) and Stirling (Hayford Mills, Cambusbarren)
Northern Command – Newcastle, York and Morpeth
Emergency Scheme (B) - Reinforcement of Central Force north of the Thames
Arrangements were put in hand to reinforce Central Force if a raid in force took part anywhere on the east coast of England with troops stationed at the training centres of Aldershot and Salisbury Plain.
The regulating stations provisionally chosen were Acton Wells Junction or Willesdon. Eleven areas were designated where detraining would likely be required:
Area 1 – Bedford
Area 2- Wellingborough
Area 3 – Luton (Midland Railway)
Area 4 – St Albans
Area 5 – Hertford
Area 6 – Cambridge
Area 7 – Newmarket
Area 8 – Biggleswade
Area 9 – Boxmoor
Area 10 – Harrow
Area 11- Leighton Buzzard
Emergency Scheme (D) - Occupation of the West Flank of the London Defence Positions (North and South)
Should the need arise, arrangements were in place to bring up reinforcements composed of five Special Infantry Brigades (a total of 24 Infantry Battalions) and a Reserve Artillery Brigade to man parts of the London Defence Positions. These Special Infantry Brigades would be found from Garrison troops (Portsmouth, Portland, Plymouth, Milford, Cardiff, Mersey and Barrow). As soon as it was decided to bring up the reinforcements, warning orders would be issued to the General Officers Commanding-in-Chief of the Commands concerned, who would then pass on the order to the Officers Commanding the Garrisons. Infantry units were to be prepared to move 12 hours after receipt of the warning.
Infantry would proceed to designated entraining stations. Brigade HQ would travel on the first train allotted to the Brigade. The regulating station for the Northern Positions was Victoria Park and the detraining stations Chipping Ongar and Epping. For the Southern Positions, the regulating station was Raynes Park and the detraining stations were Epsom and Leatherhead. A certain amount of transport was to be entrained with the infantry; additional transport would be allocated at the detraining stations at the scale of three GS wagons with drivers per battalion. Infantry was to carry with them three days rations and three days ration per horse. Small arms ammunition was also to be taken by each unit. Infantry would proceed to positions as directed by the War Office, when they would then come under the command of the General Officer Commanding-in-Chief Central Force.
The Reserve Artillery Brigade designated was No.4a Reserve Brigade, R.F.A., stationed at Woolwich, which had been organised as a Special Brigade of four batteries. The Brigade had 100 rounds per gun already issued, and further ammunition to complete 176 rounds per gun would be issued if available. The Brigade was to be ready to move six hours after the issue of the warning, which was to be sent by General Officer Commanding-in-Chief Central Force.
Reorganisation of Home Defence Forces
Towards the end of 1915 and the beginning of 1916, a number of changes were made to Home Defence arrangements necessitated by the increasing demands for troops required overseas, which took priority over Home Defence. The most important changes to Home Defence arrangements were:
The formation of GHQ Home Forces to take over all aspects of Home Defence planning and administration. This left the War Office to fully concentrate on the campaigns overseas. The training of troops at home, which were to form the drafts for overseas, was still carried out under the administration of the various Commands under the instructions of the War Office.
The reduction of Home Defence Armies from three to two (now designated Northern Army, based north of the Thames and Southern Army, based south of the Thames).
Central Force was disbanded and its administrative arrangements amalgamated into Eastern Command; it had been found that arrangements where Central Force acted as an independent Army within the area under Eastern Command was unworkable.