Despite the frantic defence construction on the Continent in the 1930s, with fortifications such as the Maginot Line and the West Wall, it was not until 1940, after the defeat at Dunkirk, that similar activity was prompted in Britain. The Royal Navy had only updated a few of its coastal forts since the First World War and the main improvements in defence had been the increase in magnitude of air defence. A Home Defence Executive was formed under General Sir Edmund Ironside to organise the island’s defences; a plan was immediately put into effect.
The plan was based on an ‘extended crust’ theory. This meant that the first line of defence would be along the probable invasion beaches. Behind this, in the stop-lines, troops were to be stationed at nodal points - formidable tactical areas designed to offer a threat to the flanks and rear of any force breaking through the stop-line - where they would use road blocks and any available obstructions to stop or at least delay the advancing German armoured columns. The last line of defence was the GHQ Stop-Line protecting London and the industrial Midlands.
The defences themselves consisted of various types of structure - pillboxes, gun emplacements, coastal batteries - as well as a wide range of minefields, barbed wire, anti-tank obstacles and trenches. For the most part these were constructed of reinforced concrete and brick although there were several local variations depending on available materials. The War Office Directorate of Fortifications and Works issued standardised designs for these defences but in the majority of cases these were adapted in the field to suit local tactical considerations.
The sites along the Somerset coast were all built by private contractors. They were mainly grouped around harbours and along open beaches to prevent the enemy from using adjoining roads and railways to drive inland. The defences were built until 1941 when it was realised that the Germans had missed their chance for invasion and at the end of the war in 1945 farmers on whose land the defences had been built were paid £5 for each one they could demolish.