page_title: British anti-invasion preparations of the Second World War
section_title: Field fortifications
hierarchical_section_title: British anti-invasion preparations of the Second World War / Field fortifications
caption_attribution_description: English: Coast Defence Battery - September 1940 image: A coastal heavy artillery emplacement, probably at Grain Fort, which defended the Rivers Thames and Medway. The emplacement is covered by camouflage netting overlooking the sea, which is visible on the left. The large calibre gun, in the centre left, is also camouflaged with paint in shades of green, brown and yellow. The emplacement is constructed from concrete. All is set against a cloudy blue sky.
context_page_description: British anti-invasion preparations of the Second World War entailed a large-scale division of military and civilian mobilisation in response to the threat of invasion by German armed forces in 1940 and 1941. The British Army needed to recover from the defeat of the British Expeditionary Force in France, and 1.5 million men were enrolled as part-time soldiers in the Home Guard. The rapid construction of field fortifications transformed much of the United Kingdom, especially southern England, into a prepared battlefield. Sea Lion was never taken beyond the preliminary assembly of forces. Today, little remains of Britain's anti-invasion preparations; only reinforced concrete structures such as pillboxes and anti-tank cubes are commonly found.
context_section_description: The British engaged upon an extensive programme of field fortification.
  On 27 May 1940 a Home Defence Executive was formed under General Sir Edmund Ironside, Commander-in-Chief, Home Forces, to organise the defence of Britain. At first defence arrangements were largely static and focused on the coastline (the coastal crust) and, in a classic example of defence in depth, on a series of inland anti-tank 'stop' lines. The stop lines were designated Command, Corp and Divisional according to their status. The longest and most heavily fortified was the General Headquarters anti-tank line, GHQ Line, which ran across southern England, wrapped around London and then ran north to Yorkshire. It was intended to protect the capital and the industrial heartland of England. Another major line was the Taunton Stop Line, which defended against an advance from England's south-west peninsula. London and other major cities were ringed with inner and outer stop lines. Some 50 known stop lines were constructed in Britain, though some of the less important lines were just demolition belts and not all lines were completed.
  Military thinking shifted rapidly. Given the lack of equipment and properly trained men, Ironside had little choice but to adopt a strategy of static warfare, but it was soon perceived that this would not be sufficient. Ironside has been criticised for having a siege mentality, but some consider this unfair, as he is believed to have understood the limits of the stop lines and never expected them to hold out indefinitely.
  Churchill was not satisfied with Ironside's progress, especially with the creation of a mobile reserve. Anthony Eden, the Secretary of State for War, suggested that Ironside should be replaced by General Alan Brooke (later Viscount Alanbrooke). On 17 July 1940 Churchill spent an afternoon with Brooke and was soon convinced that they were in close agreement as to how best to defend the nation. On 19 July Brooke replaced Ironside.
  Brooke's appointment coincided with more trained men and better equipment becoming available. Under Brooke, new strategies and tactics were devised. More concentration was placed on defending the coastal crust, while inland a hedgehog defence strategy of defended localities and anti-tank islands was established, each having all-round defence. Many of these anti-tank islands were established along the already constructed stop lines, where existing defences could be integrated into the new strategy and, especially, at towns and villages where there was a Home Guard to provide personnel.
caption: British coastal artillery in September 1940, painting by Barnett Freedman
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