Excavations started on 28 December 1940 and the first gun arrived on 25 March 1941, although their best-known action came a few months later, on 12 February 1942, when the light battleships Gneisenau, Scharnhorst and the heavy cruiser Prinz Eugen attempted the Channel Dash from Brest back to Germany. The K band radar at South Foreland started to track the ships of the Brest Group coming up the Channel towards Cap Gris Nez. At 12:19, the first salvo was fired; since maximum visibility was five miles, there was no observation of fall of shot by either sight or radar. The "blips" of the K-set clearly showed the zig-zagging of the ships and full battery salvo firing began without verifying fall-of-shot. 33 rounds were fired at the German ships, which were moving out of range at 30 kn (35 mph; 56 km/h).

 Initially it was thought that four hits had been made, but the Germans revealed that all had missed. By the end of the war the four guns had expended 2,248 shells, most in the months before and after the Normandy landings. 28 enemy ships were confirmed sunk between all the coastal batteries around Dover and the deterrent effect was significant

Situated on the cliffs between Dover & St. Margaret’s, this was the heaviest gun battery installed along Kent’s coastline during WWII. It consisted of 2 x 15” Naval guns supplied, along with their mountings and power plants, by the Admiralty. The War Office assumed responsibility for all the building work on the site including the laying of railway tracks which connected to the main Dover to Deal line at Martin Mill. The installation of the guns and construction of the ancillary buildings, magazines, underground plotting room and shelters was completed on 19th May 1942 when they were handed over to the Army to be manned by men from 540 Coast Defence Regiment. The huge guns were soon blessed with the nicknames ‘Jane’ (after a popular newspaper cartoon character of the time) and ‘Clem’ (after the then Deputy PM – Clement Atlee). Apart from their basic armoured housings the only passive protection afforded to the guns was the reverse-slope of their emplacements and some heavy camouflage netting. However a HAA battery was installed nearby which offered substantial offensive protection from air attack. The Battery continued in service after the War, as part of the Coast Training Regiment, until the mid 1950’s when it was de-commissioned and the guns dismantled.

Credit to Kent's Historic Sights

When German Panzers rolled into the French coastal region around Calais in late May 1940, their crews could stare across the English Channel at the White Cliffs of Dover, just 20 miles away.

The United Kingdom had not faced a hostile enemy across the Channel since the Napoleonic Wars. In that interval, the maximum range of heavy artillery had increased dramatically. Hitler was alert to the opportunity this afforded him for his planned invasion of Britain, dubbed Operation Sea Lion.

“Strong forces of coastal artillery must command and protect the forward coastal area,” Hitler wrote in a July 16 invasion plan. He wanted the batteries not only to protect his invasion force from the Royal Navy, but to bombard the British defenders on the opposite shore.

The big guns began to arrive a week later, accompanied by work crews to build giant concrete casements to protect them from counter-bombardment. The best were turreted naval guns originally designed for use on battleships that could track and fire rapidly to hit moving ships.

At Cape Gris Nez, the Germans mounted four intimidating 380-millimeter SK34 naval guns of Battery Todt in enormous concrete casemates. Nearby were the four 280-millimeter guns of the Grosser Kurfurst battery.

On Cape Blanc Nez, the beach immediately west of Calais, three 406-millimeter “Adolf Cannons” were installed in casemates shielded by 13 feet of concrete. These could lob one-ton shells up to a distance of 34 miles. 

Four more turreted coastal guns were installed around Calais, and three 305-millimeter naval guns with a 32 mile range were deployed near the city of Boulogne to the south. The Wehrmacht also brought eight railway guns and 40 army siege guns into the Calais region. These ranged from 21 to 28 centimeters in caliber. However, they lacked the ability to rapidly adjust fire to strike moving maritime targets.