Field Service Regulations 1935 again highlights the importance of depth in any defensive position. It points out that the enemy with modern weapons and by concenrtating his force at a particular point will always be able to achieve a breakthrough on a limited front. A defence in depth will be able to halt/slow down the enemy advance and enable a counter attack to develop.
The manual also highlights that a defence should be based on fire rather than men - the co-ordinated fire of all weapons. The organisation of the defence is then outlined in this manual and Infantry Training 1937.
The 1937 manual describes the organised defence of consisting of "a belt of defended localities arranged in depth and affording mutual support. The belt of foremost defended localities becomes the front edge of the defensive system and the defence is built up in depth in rear of it”. The manual goes on to describe in essence the role of forward and battle zones (although these terms are not used): “In front of the line of foremost defended localities is a co-ordinated belt of fire of all arms to break up the enemy assault; and behind this, fire is organized in depth to stop any of the enemy who may succeed in penetration of the foremost belt, until they can be captured or driven from the defences.” The defence would be developed through the initial siting of weapons pits, linking these with crawl trenches and finally a fully developed trench system if the defence became protracted.
Development of a defensive system, RE Pocket Book, Pamphlet IV - Defences 1936
The basic concept of stop-lines (although again this terminology is not used) can also be found in this manual: “Obstacles may be used in two ways, as protective obstacles to check an attack under the fire of the defence so that it may be stopped by fire, or as tactical obstacles to restrict the freedom of manoeuvre of an attack and to herd it into pockets, when it can be effectively dealt with by the fire of the defence”. In particular, with regard to anti-tank defence, “the passive means of [anti-tank] defence include the use of natural obstacles (such as woods, streams, marshy ground), of the protection afforded by buildings (or by blockhouses specially constructed when time is available) and the construction of artificial obstacles of various types”. Field Service Regulations Vol II also make reference to the front being covered with “a continuous tank obstacle (trenches or minefields or other obstacles)”.
Military Training Pamphlet No.23 Part II Defence, published in 1939, contained the latest ideas in the subjects dealt with in Field Service Regulations 1935. Of interest is the following: "It is often advisable to construct only a nucleus of the system [of defence], preference being given to work that takes time, e.g. concrete cover". This pamphlet has much to say on anti-tank defence. Again, the concept of stop-lines is outlined: "River lines are attractive as providing an unmistakable obstacle behind which the defence can be organized" and "Railway lines, if passing through a series of cuttings and over steep embankments often provide useful obstacles". This pamphlet also acknowledges a growing recognition of the value of air power in defence.
Field Service Regulations Vol II, HMSO, 1935
Infantry Training, HMSO, 1937
Operations - Military Training Pamphlet No.23 Part II Defence,HMSO, 1939