After the Fall of France in June 1940, Adolf Hitler personally discussed the possibility of invasion with Großadmiral (Grand Admiral) Erich Raeder, the Commander-in-Chief of the Kriegsmarine (German Navy) on 21 May 1940.

Almost a month later on 25 June he ordered Oberkommando der Wehrmacht (OKW, supreme command of the armed forces) to begin preparation and feasibility studies, which had to be completed by 2 July, for the invasion of Britain.

Fire control for these guns was provided by both spotter aircraft and by DeTeGerät radar sets installed at Blanc-Nez and Cap d’Alprech.

These units were capable of detecting targets out to a range of 40 km (25 mi), including small British patrol craft near the English coast.

On 24 June 1944, the convoy left Southend en route to the Seine Bay when the ships were engaged by German long-range coastal artillery guns off Dover.

Having withdrawn in the Dunkirk evacuation and winning the Battle of Britain, the British did not have an immediate answer to the threat posed by the German coastal batteries.

Both conducted extreme range counter-battery operations against the Germans' coastal guns but they were too inaccurate and slow to fire on enemy shipping.

Also, three BL 13.5-inch (343 mm) Mk V naval guns from the First World War (named Gladiator, Scene Shifter and Piece Maker [sic]) were brought out of retirement in 1939 and mounted on railway chassis.

British coastal convoys had to pass through the bottleneck of the Dover strait to transport supplies, particularly coal; Britain's road and rail network was not then able to cope with the volume of traffic that had to be handled.

[9] On 11 February 1942, the German battleships Scharnhorst and Gneisenau, the heavy cruiser Prinz Eugen and more than twenty smaller escort vessels sailed from Brest in Brittany to their home port of Wilhelmshaven by an audacious dash through the English Channel, codenamed Unternehmen Zerberus (Operation Cerberus).

As the visibility was only 5 nmi (5.8 mi; 9.3 km), it was hoped that the radar would be able to register the splashes as the shells landed so that the guns would be able to correct their aim but nothing was detected.

[11] Accurate bombardment from the British heavy guns at Dover disabled the Grosser Kurfürst Battery at Floringzelle near Cap Gris Nez, ending the duels.

One of the casemates of the Todt Battery can be visited at the Musée du Mur de l'Atlantique, the Atlantic Wall Museum, at Audinghen.