Trench systems dug for Home Defence developed as strong points, consisting of small posts to closed group of fire trenches suitable for anything from a few rifles up to 400 rifles. The most complex closed trench systems contained fire, communication and cover trenches; head cover was often provided in the fire trench and short stretches of overhead cover provided along communication and cover trenches. Splinter-proof shelters were also provided. Traverses were constructed to give protection against enfilade rifle fire and to minimise the effect of shell burst inside a trench.
Communication trenches allowed men to move around the defence under cover. They were often provided with a parapet on both sides and traverses. Some were given overhead cover.
Cover trenches were provided to give protection for men not in the firing line using their rifles.
Should a higher command be required to cover the ground in front, or in soils with a high water table, the parapet had to be raised – such works were referred to as breastworks.
If head cover was provided, some form of loophole was required. This reduced the number of rifles that could be put in the line and also the field of fire but it increased the sense of security felt and hence the accuracy of the rifle fire. Loopholes were constructed from sandbags, sacks or boxes filled with earth or gravel – shingle was a ready to hand material in Suffolk. The minimum height of the interior of loopholes was 18 inches, to allow the rifleman to get their head well forward and under the head cover. When constructed, each loophole had to be tested with a rifle to ensure fields of fire were not too restricted. When not in use, loopholes were blinded with grass etc.
A shingle loophole was constructed as follows: one sandbag was placed inside another, and the interior sandbag filled with shingle. Three double sandbags would be sufficient to construct the loophole. They were then placed in position and hammered or stamped out until the opening was curved. The rest of the head cover was constructed with earth, revetted with shingle filled sandbags.
Above: Left - trench shelter and communication trench.
Middle - loopholes
Right - shingle loopholes
Drainage in trenches was important. This was usually provided by sloping the bottom of the trench to a gully at the back of the trench, which drained into a soak pit or was let off at lower ground.
Overhead cover was time consuming to construct but provided protection against heavy shrapnel fire, hand grenades and bombing from aircraft. It normally consisted of about 9 to 12 inches of earth or about 3 inches of shingle supported on boards or corrugated iron.
Splinter-proof shelters were also provided. Care had to be taken not to weaken the parapet or reduce the number of men in the firing line. Numerous small shelters were better than a few elaborate shelters.
Field redoubts were also constructed, in Suffolk at least in the defence of the defended port of Harwich. A redoubt is an earthwork entirely enclosed by a defendable parapet which gave all round rifle fire.
Closed systems of trenches and field redoubts were designed to be elastic in defence in terms of varying the number of rifles to suit the conditions while at the same time remaining self contained.
Machine gun emplacements
In the defence, machine guns operated best if sited in concealed prepared positions to provide powerful enfilade or oblique fire on the ground attackers must cross after they have reached effective infantry range, to provide flanking fire for supporting works or to sweep gaps left in obstacles. When located in a trench, a platform would need to be constructed for the gun. The crest of such as emplacement could take the form of an arc, the length depending on the field of fire of the gun. Head cover could be provided.
Hedges and banks
Hedges and banks which interfered with the field of fire or could conceal enemy movements should be removed. They could also be easily prepared for defence if a ditch existed on the defenders side or by digging a ditch and placing the spoil against the hedge. In the Felixstowe position hedges and banks were prepared for defence in such a manor – e.g. Golf Club House position.
Walls and fences could be demolished to improve fields of fire. Walls could also be utilised for defence to give protection from rifle fire. A wall of between 4 ft and 4ft 6 ins the could be used as it stands. Below 4 ft high, a small trench could be dug. Between 5 ft and 6ft a wall could be notched but above 6 ft a stage would have to be provided or the wall loopholed. Loopholes were preferable to a notched wall as they provided head cover. Loopholes should not be closer together than 3 ft from centre to centre. Holes could be made with crowbars, picks or a mason’s chisel and should be as small as possible on the outside to lessen the chance of bullets entering. Loopholed walls were certainly part of the Felixstowe defences.
If not subject to heavy artillery fire, buildings were of great defensive value. Buildings were prepared for defence by the provision of bullet proof barricades to doors and windows. The barricades were loopholed as they were easier to loophole than the walls of the building. Many buildings in towns along the East Coast were requisition and prepared for defence in such a way.
For close defence of ports and other strategical sites, blockhouses were constructed as part of the defences. These varied from designs similar to those used in South Africa, consisting of shingle between wooden boarding such as those constructed at Shoeburyness, to concrete blockhouses.
Landguard Fort was provided with several blockhouses as were nearby strategic sites such as the Naval Docks and Wireless Station. These were probabaly simple designs such as those at Shoeburyness.
Above: Blockhouse designs at Shoeburyness