Editing Operation Sea Lion (section)

== German coastal guns ==
{{Main|Cross-Channel guns in the Second World War}}
With Germany's occupation of the [[Pas-de-Calais]] region in northern [[France]], the possibility of closing the [[Strait of Dover]] to Royal Navy warships and merchant convoys by the use of land-based heavy artillery became readily apparent, both to the German High Command and to Hitler. Even the ''Kriegsmarine'''s Naval Operations Office deemed this a plausible and desirable goal, especially given the relatively short distance, {{convert|34|km|abbr=on}}, between the French and English coasts. Orders were therefore issued to assemble and begin emplacing every Army and Navy heavy artillery piece available along the French coast, primarily at Pas-de-Calais. This work was assigned to the ''[[Organisation Todt]]'' and commenced on 22 July 1940.<ref name=Schenk323>Schenk, p. 323</ref>
[[File:210 mm Railway Gun.jpg|thumb|right|The huge [[21 cm K 12 (E)|21 cm K12 railway gun]] was only suitable for bombarding targets on land.]]
By early August, four {{convert|28|cm|abbr=on}} traversing turrets were fully operational as were all of the Army's railway guns. Seven of these weapons, six 28&nbsp;cm [[Krupp K5|K5 pieces]] and a single {{convert|21|cm|abbr=on}} [[21 cm K 12 (E)|K12 gun]] with a range of {{convert|115|km|abbr=on}}, could only be used against land targets. The remainder, thirteen 28&nbsp;cm and five {{convert|24|cm|abbr=on}} pieces, plus additional motorised batteries comprising twelve 24&nbsp;cm guns and ten 21&nbsp;cm weapons, could be fired at shipping but were of limited effectiveness due to their slow traverse speed, long loading time and ammunition types.<ref name=Schenk324>Schenk, p. 324</ref>

Better suited for use against naval targets were the four heavy naval batteries installed by mid-September: ''Friedrich August'' with three [[30.5 cm SK L/50 gun|{{convert|30.5|cm|abbr=on}} barrels]]; ''Prinz Heinrich'' with two [[28 cm SK L/40 gun|28&nbsp;cm guns]]; ''[[Battery Oldenburg|Oldenburg]]'' with two 24&nbsp;cm weapons and, largest of all, ''Siegfried'' (later renamed ''Batterie Todt'') with a pair of [[38 cm SK C/34 naval gun|{{convert|38|cm|abbr=on}} guns]]. Fire control for these weapons 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 {{convert|40|km|abbr=on}}, including small British patrol craft inshore of the English coast. Two additional radar sites were added by mid-September: a DeTeGerät at Cap de la Hague and a FernDeTeGerät long-range radar at Cap d’Antifer near Le Havre.<ref name=Schenk324-325>Schenk, pp. 324–25</ref>

To strengthen German control of the Channel narrows, the Army planned to quickly establish mobile artillery batteries along the English shoreline once a beachhead had been firmly established. Towards that end, 16th Army's ''Artillerie Kommando 106'' was slated to land with the second wave to provide fire protection for the transport fleet as early as possible. This unit consisted of twenty-four {{convert|15|cm|abbr=on}} and seventy-two {{convert|10|cm|abbr=on}} guns. About one third of them were to be deployed on English soil by the end of Sea Lion's first week.<ref name=Schenk325-327>Schenk, pp. 325–27</ref>

The presence of these batteries was expected to greatly reduce the threat posed by British destroyers and smaller craft along the eastern approaches as the guns would be sited to cover the main transport routes from Dover to Calais and Hastings to Boulogne. They could not entirely protect the western approaches, but a large area of those invasion zones would still be within effective range.<ref name=Schenk325-327 />

The British military was well aware of the dangers posed by German artillery dominating the Dover Strait and on 4 September 1940 the Chief of Naval Staff issued a memo stating that if the Germans "…could get possession of the Dover defile and capture its gun defences from us, then, holding these points on both sides of the Straits, they would be in a position largely to deny those waters to our naval forces". Should the Dover defile be lost, he concluded, the Royal Navy could do little to interrupt the flow of German supplies and reinforcements across the Channel, at least by day, and he further warned that "…there might really be a chance that they (the Germans) might be able to bring a serious weight of attack to bear on this country". The very next day the Chiefs of Staff, after discussing the importance of the defile, decided to reinforce the Dover coast with more ground troops.<ref name=Cox149-150>Cox, pp. 149–50</ref>

The guns started to fire in the second week of August 1940 and were not silenced until 1944, when the batteries were overrun by Allied ground forces. They caused 3,059 alerts, 216 civilian deaths, and damage to 10,056 premises in the Dover area. However, despite firing on frequent slow moving coastal convoys, often in broad daylight, for almost the whole of that period (there was an interlude in 1943), only one seaman was killed and others were injured by shell splinters from near misses. <ref>Hewitt, Nick p. 109</ref> Also 2 transports were sunk by them. <ref>{{Cite web |last=Baylor |first=Joshua |date=2019-03-23 |title=Guns of Navarone: How Effective was Coastal Artillery in WWII? {{!}} War History Online |url=https://www.warhistoryonline.com/instant-articles/guns-of-navarone-coastal-artillery.html |access-date=2024-04-04 |website=warhistoryonline |language=en}}</ref> Whatever the perceived risk, this lack of ability to hit any moving ship does not support the contention that the German coastal batteries would have been a serious threat to fast destroyers or smaller warships.<ref>Hewitt, Geoff p. 41</ref>  They're a threat only to landing forces at short range.<ref>{{Cite web |last=Baylor |first=Joshua |date=2019-03-23 |title=Guns of Navarone: How Effective was Coastal Artillery in WWII? {{!}} War History Online |url=https://www.warhistoryonline.com/instant-articles/guns-of-navarone-coastal-artillery.html |access-date=2024-04-04 |website=warhistoryonline |language=en}}</ref>