Operation Sea Lion
Operation Sea Lion, also written as Operation Sealion[2][3] (German: Unternehmen Seelöwe), was Nazi Germany's code name for their planned invasion of the United Kingdom. It was to take place during the Battle of Britain, nine months after the start of the Second World War. Following the Battle of France and that country's capitulation, Adolf Hitler, the German Führer and Supreme Commander of the Armed Forces, hoped the British government would accept his offer to end the state of war between the two. He considered invasion to be a last resort, to be used only if all other options had failed.[4]
This article is about the planned German invasion of Britain. For the 1974 wargame based on this plan, see Operation Sea Lion (wargame).Operation Sea Lion
Normandy, the Belgian coastline, the English Channel and the English coastline; initial Army proposals of 25 July 1940 envisaging landings from Kent to Dorset, Isle of Wight and parts of Devon; subsequently refined to a confined group of four landing sites in East Sussex and western Kent
September 1940
Elimination of the United Kingdom as a base of military operations against the Axis powers[1]
Eventual cancellation and diversion of German, Italian, and other Axis forces for Operation Barbarossa
As a precondition for the invasion of Britain, Hitler demanded both air and naval superiority over the English Channel and the proposed landing sites. The German forces achieved neither at any point of the war. Further, both the German High Command and Hitler himself held serious doubts about the prospects for success. Nevertheless, both the German Army and Navy undertook major preparations for an invasion. These included training troops, developing specialised weapons and equipment, modifying transport vessels and the collection of a large number of river barges and transport ships on the Channel coast. However, in light of mounting Luftwaffe losses in the Battle of Britain and the absence of any sign that the Royal Air Force had been defeated, Hitler postponed Sea Lion indefinitely on 17 September 1940. It was never put into action.
Air power[edit]
Airborne forces[edit]
The success of the German invasion of Denmark and Norway, on 9 April 1940, had relied extensively on the use of paratroop and glider-borne formations (Fallschirmjäger) to capture key defensive points in advance of the main invasion forces. The same airborne tactics had also been used in support of the invasions of Belgium and the Netherlands on 10 May 1940. However, although spectacular success had been achieved in the airborne assault on Fort Eben-Emael in Belgium, German airborne forces had come close to disaster in their attempt to seize the Dutch government and capital of The Hague. Around 1,300 of the 22nd Air Landing Division had been captured (subsequently shipped to Britain as prisoners of war), around 250 Junkers Ju 52 transport aircraft had been lost, and several hundred elite paratroops and air-landing infantry had been killed or injured. Consequently, even in September 1940 the Luftwaffe had the capacity to provide only around 3,000 airborne troops to participate in the first wave of Operation Sea Lion.
Army[edit]
Panzers ashore[edit]
Providing armour support for the initial wave of assault troops was a critical concern for Sea Lion planners, and much effort was devoted to finding practical ways of rapidly getting tanks onto the invasion beaches in support of the first echelon. Though the Type A barges could disembark several medium tanks onto an open beach, this could be accomplished only once the tide had fallen further and the barges were firmly grounded along their full length; otherwise, a leading tank might topple off an unsteady ramp and block those behind from deployment. The time needed for assembling the external ramps also meant that both the tanks and the ramp assembly crews would be exposed to close-quarter enemy fire for a considerable time. A safer and faster method was needed, and the Germans eventually settled on providing some tanks with floats and making others fully submersible. It was nevertheless recognised that a high proportion of these specialised tanks might be expected not to make it off the beach.
Broad versus narrow front[edit]
The German Army High Command (Oberkommando des Heeres, OKH) originally planned an invasion on a vast scale, envisioning landing over forty divisions from Dorset to Kent. This was far in excess of what the Kriegsmarine could supply, and the final plans were more modest, calling for nine divisions to make an amphibious assault on Sussex and Kent with around 67,000 men in the first echelon and a single airborne division of 3,000 men to support them.[91] The chosen invasion sites ran from Rottingdean in the west to Hythe in the east.
The Kriegsmarine wanted the front to be as short as possible, as it regarded this as more defensible. Admiral Raeder wanted a front stretching from Dover to Eastbourne and stressed that shipping between Cherbourg/Le Havre and Dorset would be exposed to attacks from the Royal Navy based in Portsmouth and Plymouth. General Halder rejected this: "From the army's point of view I regard it as complete suicide, I might just as well put the troops that have landed straight through the sausage machine".[92]
One complication was the tidal flow in the English Channel, where high water moves from west to east, with high water at Lyme Regis occurring around six hours before it reaches Dover. If all the landings were to be made at high water across a broad front, they would have to be made at different times along different parts of the coast, with the landings in Dover being made six hours after any landings in Dorset and thus losing the element of surprise. If the landings were to be made at the same time, methods would have to be devised to disembark men, vehicles and supplies at all states of the tide. That was another reason to favour landing craft.
Indefinite postponement[edit]
During the summer of 1940, both the British public and the Americans believed that a German invasion was imminent, and they studied the forthcoming high tides of 5–9 August, 2–7 September, 1–6 October, and 30 October – 4 November as likely dates.[102] The British prepared extensive defences, and, in Churchill's view, "the great invasion scare" was "serving a most useful purpose" by "keeping every man and woman tuned to a high pitch of readiness".[103][104] He did not think the threat credible. On 10 July, he advised the War Cabinet that the possibility of invasion could be ignored, as it "would be a most hazardous and suicidal operation"; and on 13 August that "now that we were so much stronger", he thought "we could spare an armoured brigade from this country". Over-riding General Dill, Churchill initiated Operation Apology by which a series of troop convoys, including three tank regiments and eventually the entire 2nd Armoured Division, were sent around the Cape of Good Hope to reinforce General Wavell in the Middle East in support of operations against Italian colonial forces (Italy had declared war on 10 June).[105] Furthermore, on Churchill's urging, on 5 August the War Cabinet approved Operation Menace, in which a substantial proportion of the Home Fleet – two battleships, an aircraft carrier, five cruisers, and twelve destroyers, together with five out of six battalions of Royal Marines, were dispatched to Dakar on 30 August in an attempt to neutralise the battleship Richelieu and detach French West Africa from Vichy France to the control of the Free French. Overall, these actions demonstrated Churchill's confidence that the immediate danger of a German invasion was now over.[106]
The Germans were confident enough to film a simulation of the intended invasion in advance. A crew turned up at the Belgian port of Antwerp in early September 1940 and, for two days, they filmed tanks and troops landing from barges on a nearby beach under simulated fire. It was explained that, as the invasion would happen at night, Hitler wanted the German people to see all the details.[107]
In early August, the German command had agreed that the invasion should begin on 15 September, but the Navy's revisions to its schedule set the date back to 20 September. At a conference on 14 September, Hitler praised the various preparations, but told his service chiefs that, as air superiority had still not been achieved, he would review whether to proceed with the invasion. At this conference, he gave the Luftwaffe the opportunity to act independently of the other services, with intensified continuous air attacks to overcome British resistance; on 16 September, Göring issued orders for this new phase of the air attack.[108] On 17 September 1940, Hitler held a meeting with Reichsmarschall Hermann Göring and Generalfeldmarschall Gerd von Rundstedt during which he became convinced the operation was not viable. Control of the skies was still lacking, and co-ordination among three branches of the armed forces was out of the question. Later that day, Hitler ordered the postponement of the operation. He ordered the dispersal of the invasion fleet in order to avert further damage by British air and naval attacks.[109]
The postponement coincided with rumours that there had been an attempt to land on British shores on or about 7 September, which had been repulsed with large German casualties. The story was later expanded to include false reports that the British had set the sea on fire using flaming oil. Both versions were widely reported in the American press and in William L. Shirer's Berlin Diary, but both were officially denied by Britain and Germany. Author James Hayward has suggested that the whispering campaign around the "failed invasion" was a successful example of British black propaganda to bolster morale at home and in occupied Europe, and convince America that Britain was not a lost cause.[110]
On 12 October 1940, Hitler issued a directive releasing forces for other fronts. The appearance of preparations for Sea Lion was to be continued to keep political pressure on Britain, and a fresh directive would be issued if it was decided that invasion was to be reconsidered in the spring of 1941.[111][112] On 12 November 1940, Hitler issued Directive No. 18 demanding further refinement to the invasion plan. On 1 May 1941, fresh invasion orders were issued under the codename Haifische (shark), accompanied by additional landings on the southwest and northeast coasts of England codenamed Harpune Nord and Harpune Süd (harpoon north and south), although commanders of naval stations were informed that these were deception plans. Work continued on the various amphibious warfare developments such as purpose-built landing craft, which were later employed in operations in the Baltic.[113]
While the bombing of Britain intensified during the Blitz, Hitler issued his Directive No. 21 on 18 December 1940 instructing the Wehrmacht to be ready for a quick attack to commence his long planned invasion of the Soviet Union.[114] Seelöwe lapsed, never to be resumed.[115] On 23 September 1941, Hitler ordered all Sea Lion preparations to cease, but it was 1942 before the last of the barges at Antwerp were returned to trade. Hitler's last recorded order with reference to Sea Lion was on 24 January 1944, reusing equipment that was still stockpiled for the invasion and stating that twelve months' notice would be given of its resumption.[116]