The nature of the beach defences that sprang up in the summer of 1940, along with strategical thinking throughout the War, was in accordance with pre-War manuals.
“Engineer Training 1937” outlines both the startegical and tactical nature of beach defence. The strategical and tactical circumstances of the defence of a stretch of coast could vary considerably. Britain had insufficient troops to defend its long coast line. On the other hand not all stretches of coast were suited for landings either due to marine conditions (depth of water, currents, rocks etc.), difficulty of inland communications from the beaches to enemy objectives (for example marshes to rear of the beaches) or the need for the enemy to secure sea communications (i.e. distance from enemy naval and air bases). Thus should troops be distributed to cover all beaches suitable for landing or concentrated on those most likely to be subject to enemy landings? In either case early warning of any landing would always be necessary, by means of naval and air patrols, coastal watchers etc.
“Engineer Training 1937” notes that the arrangements required for the defence of beaches differed from the normal defensive systems in land operations. The defence of beaches favored a linear defence for two reasons: