page_title: British anti-invasion preparations of the Second World War
section_title: Offensive anti-invasion operations
hierarchical_section_title: British anti-invasion preparations of the Second World War / Offensive anti-invasion operations
caption_attribution_description: English: IWM caption&#160;: Blenheim Mark IV, R3612 ‘BL-V’, of No. 40 Squadron RAF based at Wyton, Huntingdonshire, in flight. R3612 previously served with the Photographic Development Unit. It was lost with its entire crew on 8/9 September 1940 during a night raid on invasion barges at Ostend.
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 War Cabinet and the Chiefs of Staff Committee were not content to sit and wait for the Germans to make the first move; considerable efforts were to attack, by air and sea, the enemy shipping which had been assembled in occupied ports between The Hague and Cherbourg, starting in July 1940. These attacks became known as the "Battle of the Barges". Some notable operations are shown below:
  12 August: Five Handley Page Hampdens attacked the Ladbergen Aqueduct on the Dortmund-Ems Canal. The waterway was blocked for ten days, impeding the movement of barges towards the Channel ports.
  8 September: Two cruisers and ten destroyers swept along the French coast and bombarded Boulogne harbour. In a separate operation, three Motor Torpedo Boats attacked a convoy of small vessels off Ostend; two of the MTBs then entered the harbour and torpedoed two transport ships.
  10 September: Three destroyers found a convoy of invasion transports off Ostend and sank an escort vessel, two trawlers that were towing barges and one large barge.
  13 September: Three destroyers sent to bombard Boulogne but the operation was cancelled due to bad weather. A further twelve destroyers swept parts of the French coast.
  15 September: Sergeant John Hannah gained the Victoria Cross during a raid by RAF bombers on invasion barges at Antwerp; four transport ships were damaged.
  17 September: A major attack by Bomber Command on ports along the occupied coast. 84 barges were damaged at Dunkirk.
  26 September: Operation Lucid, a plan to send fire ships into the harbours at Calais and Boulogne to destroy invasion barges, was abandoned when one of the old tankers that were to be used had engine failure.
  30 September: The monitor HMS Erebus fired seventeen 15-inch shells onto Calais docks.
  4 October: Second attempt at Operation Lucid, this time cancelled because of bad weather.
  7 October: Third attempt at Lucid, cancelled when the destroyer carrying the force commander hit a mine and had to be towed home.
  10–11 October: Operation Medium, the bombardment of invasion transports in Cherbourg. During the 18 minute bombardment, 120 15-inch shells were fired by the battleship HMS Revenge, and a total of 801 4.7-inch shells were fired by her escorting destroyers. German coastal artillery replied for 30 minutes without hitting any of the warships.
  Between 15 July and 21 September, German sources stated that 21 transport vessels and 214 barges had been damaged by British air raids. These figures may have been under-reported.
caption: This Blenheim Mark VI bomber of No. 40 Squadron RAF was lost with its crew during a raid on German invasion barges at Ostend on 8 September 1940.
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