Although this manual deals mainly with the practical construction elements of field engineering it does contain some detail on defence tactics and is a good link between the end of the Great War and Field Service Regulations 1935/Infantry Training 1937.
The manual states that one of the key aspects of defence is that depth "is essential to resist an attack supported by modern weapons". Machine guns and artillery were to be the framework of the defence and the manual also states that "full consideration must also be given to anti-tank defence". The infantry defence would have consisted of a series of defended localities, sufficiently large enough for a platoon or larger unit, sited in depth.
The manual goes on to state that infantry will be distributed in positions "from which they can best develop the fire power of their weapons. This will ususlly result in the holding of a chain of localities mutually supporting each other by frontal, flanking or enfilade fire, and covered by the fire of the longer ranging weapons echelonned behind them. Behind these localities, reserves will be distributed in depth for the purposes of counter attack". Machine guns would ideally be sited in enfilade so their fire would sweep the flanks and front of these localities.
Infantry defences should be sited with full consideration to anti-tank obstacles (eg woods, rivers, marshes etc). Examples are given in the manual of artificial obstacles, for example mines, ditches 10 ft wide and 6 ft deep and 2 ft cube concrete blocks at 5 ft intervals.
The defence would be organised into a forward zone - a line of sentry posts with a series of defended localities in the rear arranged in depth - to warn of enemy attacks and absorb the first shock of attack. The main zone will be the area where the enemy's atttack is to be broken and again will be orgainised in depth.
If the defence was to become protracted the defended localities would be joined up with communication trenches.
Defended Locality - "an area of ground organised for defence by a definite unit such as a platoon, company or battalion". They will comprise of a series of defended posts sited for all round fire.
Defended Post - "a group of trenches or shell-holes suitable for a section or coresponding unit".
Defended posts - Manual of Field Works, 1925 Defended Locality - Manual of Field Works, 1925
Manual of Field Works (All Arms), HNSO, 1925.