Operation Sea Lion

Operation Sea Lion
Part of Western Front of World War II
The original German plan.
Operational scope Normandy, the Belgian coast line, the English Channel and the English coast line from Kent to Dorset, Isle of Wight and parts of Devon, but principally in Sussex and Kent.
Planned September 1940
Planned by OKW
Objective Elimination of the English home country as a base of military operations against the German Reich [1]
Outcome Eventual cancellation and diversion of German forces for Operation Barbarossa

Operation Sea Lion (German: Unternehmen Seelöwe) was Germany's plan to invade the United Kingdom during World War II, beginning in 1940. To have had any chance of success, however, the operation would have required air supremacy over the English Channel. With the German defeat in the Battle of Britain, Sea Lion was postponed indefinitely on 17 September 1940 and never carried out.[2]

Contents

Background

By early November 1939, Adolf Hitler had decided on forcing a decision in the West by invading Belgium, Holland and France. With the prospect of the Channel ports falling under Kriegsmarine (German Navy) control and attempting to anticipate the obvious next step that might entail, Grand Admiral (Großadmiral) Erich Raeder (head of the Kriegsmarine) instructed his Operations officer, Kapitän Hans Jürgen Reinicke, to draw up a document examining "the possibility of troop landings in England should the future progress of the war make the problem arise." Reinicke spent five days on this study and set forth the following prerequisites:[3]

In December 1939, the German Army issued its own study paper (designated Nordwest) and solicited opinions and input from both the Kriegsmarine and Luftwaffe (German Air Force). The paper outlined an assault on England's eastern coast between the Wash and Thames rivers by troops crossing the North Sea from Low Country ports. Reichsmarschall Hermann Göring, head of the Luftwaffe, responded with a single-page letter in which he stated: "...a combined operation having the objective of landing in England must be rejected. It could only be the final act of an already victorious war against Britain as otherwise the preconditions for success of a combined operation would not be met." The Kriegsmarine response was rather more restrained but equally focused on pointing out the many difficulties to be surmounted if invading England was to be a viable option.[4]

On 16 July 1940, following Germany's swift and successful occupation of France and the Low Countries and growing impatient with Britain's indifference towards his recent peace overtures, Hitler issued Directive No. 16, setting in motion preparations for a landing in Britain. He prefaced the order by stating: "As England, in spite of her hopeless military situation, still shows no signs of willingness to come to terms, I have decided to prepare, and if necessary to carry out, a landing operation against her. The aim of this operation is to eliminate the English Motherland as a base from which the war against Germany can be continued, and, if necessary, to occupy the country completely."[5]

Hitler's directive set four pre-conditions for the invasion to occur:[6]

This ultimately placed responsibility for Sea Lion's success squarely on the shoulders of Raeder and Göring, neither of whom had the slightest enthusiasm for the venture and, in fact, did little to hide their opposition to it.[7] Nor did Directive 16 provide for a combined operational headquarters under which all three service branches (Army, Navy, Air Force) could work together under a single umbrella organization to plan, coordinate and execute such a complex undertaking (similar to the Allies' creation of SHAEF for the later Normandy landings).[8]

Upon hearing of Hitler's intentions, Italian dictator Benito Mussolini, through his Foreign Minister Count Ciano, quickly offered up to ten divisions and thirty squadrons of Italian aircraft for the proposed invasion.[9] Hitler initially declined any such aid but eventually allowed a small contingent of Italian fighters and bombers, the Italian Air Corps (Corpo Aereo Italiano or CAI), to assist in the Luftwaffe's aerial campaign over Britain in October/November 1940.[10]

German land forces

Operation Eagle

Beginning in August 1940, the German Luftwaffe began a series of concentrated aerial attacks (designated Unternehmen Adlerangriff or Operation Eagle Attack) on targets throughout the British Isles in an attempt to destroy the RAF (Royal Air Force) and establish air superiority over Great Britain. The campaign later became known as the Battle of Britain. However, the change in emphasis of the bombing from RAF bases to bombing London turned Adler into a strategic bombing operation. This switch afforded the RAF, reeling from Luftwaffe attacks on its bases, time to pull back and regroup.

Navy

The most daunting problem for Germany in protecting an invasion fleet was the small size of its navy. The Kriegsmarine, already numerically far inferior to Britain's Royal Navy, had lost a sizable portion of its large modern surface units in April 1940 during the Norwegian Campaign, either as complete losses or due to battle damage. In particular, the loss of two light cruisers and ten destroyers was crippling as these were the very warships most suited to operating in the Channel Narrows where the invasion would likely take place.[11] The U-boats, the most powerful arm of the Kriegsmarine, were simply not suitable for operations in the relatively shallow and restricted waters of the English Channel.

Although the Royal Navy could not bring to bear the whole of its naval superiority (most of the fleet was engaged in the Atlantic and Mediterranean), the British Home Fleet still had a very large advantage in numbers. British ships were still vulnerable to enemy air attack, as demonstrated during the Dunkirk evacuation and by the later Japanese sinking of Prince of Wales and Repulse. However, the 22 miles (35 km) width of the English Channel (at its narrowest point, the average width is much greater and no traverse of the Channel would be that short) and the overall disparity between the opposing naval forces made the amphibious invasion plan risky, regardless of the outcome in the air. In addition, the Kriegsmarine had allocated its few remaining larger and modern ships to diversionary operations in the North Sea.

The French fleet, one of the most powerful and modern in the world, might have tipped the balance against Britain. However, the preemptive destruction of the French fleet by the British by an attack on Mers-el-Kébir and the scuttling of the French fleet in Toulon two years later ensured that this could not happen.

Even if the Royal Navy had been neutralised, the chances of a successful amphibious invasion across the channel were remote. The Germans had no specialised landing craft, and had to rely primarily on river barges. This would have limited the quantity of artillery and tanks that could be transported and restricted operations to times of good weather. The barges were not designed for use in open sea and even in almost perfect conditions, they would have been slow and vulnerable to attack. There were also not enough barges to transport the first invasion wave nor the following waves with their equipment. The Germans would have needed to immediately capture a port, an unlikely circumstance considering the strength of the British coastal defences around the south-eastern harbours at that time. The British also had several contingency plans, including the use of poison gas.

Landing craft

Invasion barges assembled at the German port of Wilhelmshaven

One of the more glaring deficiencies in the German Navy for mounting large-scale amphibious assaults was an almost complete lack of purpose-built landing craft. The Navy had already taken some small steps in remedying this situation with construction of the Pionierlandungsboot 39 (Engineer Landing Boat 39), a self-propelled shallow-draft vessel which could carry 45 infantrymen, two light vehicles or 20 tons of cargo and land on an open beach (unloading via a pair of clamshell doors at the bow). But by late September 1940, only two prototypes had been delivered.[12] Recognizing the need for an even larger craft capable of landing both tanks and infantry onto a hostile shore, the Navy began development of the 220-ton Marinefährprahm (MFP) but these too were unavailable in time for a landing on English soil in 1940, the first of them not being commissioned until April 1941.

The obvious solution for the Navy to assemble a large sea-going invasion fleet in the short time allotted was to convert inland river barges to the task. Towards that end, the Kriegsmarine collected approximately 2,400 barges from throughout Europe (860 from Germany, 1,200 from the Netherlands and Belgium and 350 from France). Of these, only about 800 were powered (some insufficiently). The rest required towing by tugs.[13]

Specialized landing equipment

As part of a Navy competition, prototypes for a prefabricated "heavy landing bridge" or jetty (similar in function to later Allied Mulberry Harbours) were designed and built by Krupp Stahlbau and Dortmunder Union and successfully overwintered in the North Sea in 1941/42.[14] Krupp's design won out as it only required one day to install as opposed to twenty-eight days for the Dortmunder Union bridge. The Krupp bridge consisted of a series of 32m-long connecting platforms, each supported on the seabed by four steel columns. The platforms could be raised or lowered by heavy-duty winches in order to accommodate for the tide. The German Navy initially ordered eight complete Krupp units composed of six platforms each. This was reduced to six units by the Autumn of 1941 and eventually cancelled altogether when it became apparent Sea Lion would never take place.[15]

In mid-1942, both the Krupp and Dortmunder prototypes were shipped to the Channel Islands and installed together off Alderney where they were used for unloading materials needed to fortify the island. Referred to as the "German jetty" by local inhabitants, it remained standing for the next thirty-six years until demolition crews finally removed it in 1978/79, a testament to its durability.[15]

The German Army developed a portable landing bridge of its own nicknamed Seeschlange (Sea Snake). This "floating roadway" was formed from a series of joined modules that could be towed into place to act as a temporary jetty. Moored ships could then unload their cargo either directly onto the roadbed or lower it down onto waiting vehicles via their heavy-duty booms. The Seeschlange was successfully tested by the Army Training Unit at Le Havre in the fall of 1941 and later slated for use in Operation Herkules, the proposed Italo-German invasion of Malta. It was easily transportable by rail.[15]

Specialized vehicles slated for Sea Lion included the Landwasserschlepper (LWS). Under development since 1935, this amphibious tractor was originally intended for use by Army engineers to assist with river crossings. Three of them were assigned to Tank Detachment 100 as part of the invasion and it was intended to use them for pulling ashore unpowered assault barges and towing vehicles across the beaches. They would also have been used to carry supplies directly ashore during the six hours of falling tide when the barges were grounded. This involved towing a Kässbohrer amphibious trailer (capable of transporting 10-20 tons of freight) behind the LWS.[16] The LWS was demonstrated to General Franz Halder on 2 August 1940 by the Reinhardt Trials Staff on the island of Sylt and, though he was critical of its high silhouette on land, he recognized the overall usefulness of the design. It was proposed to build enough tractors that each invasion barge could be assigned one or two of them but the late date and difficulties in mass-producing the vehicle prevented implementation of that plan.[16]

Broad vs. narrow front

The German Army High Command (Oberkommando des Heeres, or OKH) originally planned an invasion on a vast scale, extending from Dorset to Kent. This was far in excess of what their navy could supply, and final plans were more modest, calling for nine divisions to make an amphibious landing with around 67,000 men in the first echelon and an airborne division to support them.[17] The chosen invasion sites ran from Rottingdean in the west to Hythe in the east.

The battle plan called for German forces to be launched from Cherbourg to Lyme Regis, Le Havre to Ventnor and Brighton, Boulogne to Eastbourne, Calais to Folkestone, and Dunkirk and Ostend to Ramsgate. German paratroopers would land near Brighton and Dover. Once the coast was secured, they would push north, taking Gloucester and encircling London.[18] There is reason to believe that the Germans would not attempt to assault the city but besiege and bombard it.[19] German forces would secure England up to the 52nd parallel (approximately as far north as Northampton), anticipating that the rest of the United Kingdom would then surrender.

German coastal guns

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 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, 34 km (21 mi), 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 Organisation Todt and commenced on 22 July 1940.[20]

By early August, four 28 cm (11 in) traversing turrets were fully operational as were all of the Army’s railway guns. Seven of the railway guns, six 28 cm K5 guns and a single 21 cm (8.3 in) K12 gun with a range of 115 km (71 mi), could only be used against land targets. The remainder, thirteen 28 cm guns and five 24 cm (9.4 in) guns, plus additional motorized batteries comprising twelve 24 cm guns and ten 21 cm guns, could be fired at shipping but were of limited effectiveness due to their slow traverse speed, long loading time and ammunition types.[21]

Better suited for use against naval targets were the four heavy naval batteries installed by mid-September: Friedrich August with three 30.5 cm (12.0 in) guns; Prinz Heinrich with two 28 cm guns; Oldenburg with two 24 cm guns and, largest of all, Siegfried (later renamed Batterie Todt) with a pair of 38 cm (15 in) guns. 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 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.[22]

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 Kommand 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 24 15 cm (5.9 in) guns and 72 10 cm (3.9 in) guns. About one third of them were to be deployed on English soil by the end of Sea Lion’s first week.[23]

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.[23]

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.[24]

Cancellation

On 17 September 1940, Hitler held a meeting with Reichsmarschall Hermann Göring and Field Marshal Gerd von Rundstedt. Hitler became convinced that the operation was not viable. Control of the skies was lacking, and coordination among three branches of the armed forces was out of the question. Later that day, Hitler ordered the postponement of the operation.

The postponement coincided with a rumour that there had been an attempt to land on British shores at Shingle Street, but it had been repulsed with large German casualties. This was reported in the American press, and in William L. Shirer's Berlin Diary but was officially denied. British papers, declassified in 1993, have suggested this was a successful example of British black propaganda to bolster morale in Britain, America and occupied Europe.[25]

After the London Blitz, Hitler turned his attention to the Soviet Union, and Seelöwe lapsed, never to be resumed. However, not until 13 February 1942, after the invasion of Russia, were forces earmarked for the operation released to other duties.[26]

Chances of success

Drill involving a Panzer III amphibious tank meant for Sea Lion

Military historians are divided on whether Operation Sea Lion could have succeeded; some, such as Michael Burleigh and Andrew Mollo, believe it was possible. Kenneth Macksey asserts it would have only been possible if the Royal Navy had refrained from large scale intervention[27] and the Germans had assaulted in July 1940 (they were unprepared at that time),[28] while others such as Peter Fleming, Derek Robinson and Stephen Bungay believe the operation would have most likely resulted in a disaster for the Germans. Adolf Galland, commander of Luftwaffe fighters at the time, claimed invasion plans were not serious and that there was a palpable sense of relief in the Wehrmacht when it was finally called off.

During the period 19–26 September 1940, sea and wind conditions on and over the Channel where the invasion was set to take place were good overall and a crossing (even using converted river barges) was feasible provided the sea state remained at less than 4 (which, for the most part, it did). Beginning the night of 27 September, strong northerly winds prevailed, making passage more hazardous, but calm conditions returned on 11–12 October and again on 16–20 October. After 20 October, light easterly winds prevailed which would have actually assisted any invasion craft traveling from the Continent towards the invasion beaches. But by the end of October, according to British Air Ministry records, very strong southwest winds (force 8) would have prohibited any non-seagoing craft from risking a Channel crossing.[29]

There were a number of errors in German intelligence, and whilst some of these might not have caused problems, there were others (such as the inclusion of bridges that no longer existed[30] or misunderstanding the usefulness of minor British roads)[31] that would have been detrimental to German operations, and would have only added to the confusion caused by the layout of Britain's cities and the removal of road signs.[32]

Post-war wargaming of the plan

In wargames conducted at the Royal Military Academy Sandhurst in 1974, which assumed the Luftwaffe had not yet won air supremacy, the Germans were able to establish a beachhead in England by using a minefield screen in the English Channel to protect the initial assault. However, the German ground forces were delayed at the "Stop Lines" (e.g. the GHQ Line), a layered series of defensive positions that had been built, each a combination of Home Guard troops and physical barriers. At the same time, the regular troops of the British Army were forming up. After only a few days, the Royal Navy was able to reach the Channel from Scapa Flow, cutting off supplies and blocking further reinforcement. Isolated and facing regular troops with armour and artillery, the invasion force was forced to surrender.[33]

Planned occupation of Britain

According to the most detailed plans created for the planned post-invasion administration, Britain and Ireland were to be divided into six military-economic commands, with headquarters in London, Birmingham, Newcastle, Liverpool, Glasgow and Dublin.[34]

Franz Six

Had Operation Sea Lion been launched, Einsatzgruppen under Dr. Franz Six were to follow the invasion force to Great Britain to establish the New Order. Six's headquarters were to be in London, with regional task forces in Birmingham, Liverpool, Manchester and Edinburgh.[34] They were provided with a list (known as The Black Book) of 2,820 people to be arrested immediately. Six had been entrusted with the task of securing "aero-technological research result and important equipment" as well as "Germanic works of art". There is also a suggestion that he toyed with the idea of moving Nelson's Column to Berlin[35]

The RSHA planned to take over the Ministry of Information, to close the major news agencies and to take control of all of the newspapers. Anti-German newspapers were to be closed down.[36]

The OKW, RSHA and the Foreign Ministry compiled lists of those they thought could be trusted to form a new government along the lines of that in occupied Norway. The list was headed by Oswald Mosley. The RSHA also felt that Harold Nicolson might prove useful in this role.[37] OKW also expected to face armed civilian resistance, and planned to deport all men between 17 and 45 to the Reich (around 25% of the population), apart from members of the vital professions.[38]

A Channel 5 documentary broadcast on 16 July 2009 claimed that the Germans intended to restore Edward VIII to the throne in the event of a German occupation.[39][40]

It appears, based on the German police plans, that the occupation was to be only temporary, as detailed provisions for the postoccupational period are mentioned.[41]

In fiction

There is a large corpus of works set in an alternate history where the German invasion of Britain is attempted or successfully carried out (see also Axis victory in World War II). These include:

See also

References

  1. ↑ Furher Directive 16
  2. ↑ ”MHQ volume 6 Number 4, Summer 1994, Hitler’s D-Day”, David Shears
  3. ↑ Ansel, p.43
  4. ↑ Ansel, p.47-49
  5. ↑ Cox, p.159
  6. ↑ Cox, p.160
  7. ↑ Cox, p.157
  8. ↑ Cox, p.161
  9. ↑ Cox, p.158
  10. ↑ Macksey, Kenneth, Beda Fomm: The Classic Victory, p. 35. Ballantine, New York, 1971.
  11. ↑ Von der Porten, p.111
  12. ↑ Schenk, p.29
  13. ↑ Schenk, p.67
  14. ↑ Alderney at War. Brian Bonnard. 1993.ISBN 0-7509-0343-0. pp106-108. Alan Sutton Publishing Ltd.
  15. ↑ 15.0 15.1 15.2 Schenk, p.139
  16. ↑ 16.0 16.1 Schenk, p.132-133
  17. ↑ Schenk, p.231
  18. ↑ The Illustrated History of World War II by Owen Booth and John Walton. 1998. Page 70.
  19. ↑ German Invasion Plans for the British Isles 1940, Ed Rob Wheeler, Bodleian Library 2007, page 9
  20. ↑ Schenk, p.323
  21. ↑ Schenk, p.324
  22. ↑ Schenk, p.324-325
  23. ↑ 23.0 23.1 Schenk, p.325-327
  24. ↑ Cox, p.149-150
  25. ↑ Rigby, Nic (2002-09-09). "Was WWII mystery a fake?". BBC News. http://news.bbc.co.uk/1/hi/england/2243082.stm. Retrieved 2007-09-23. 
  26. ↑ Fleming, Peter.,Invasion 1940 (Readers Union, London, 1958), p. 273.
  27. ↑ Macksey 1990, pp. 144-146.
  28. ↑ Macksey 1990, pp. 209-210
  29. ↑ Cox, p. 187
  30. ↑ German Invasion Plans for the British Isles, Ed Rob Wheeler, Bodleian Library 2007, p. 10
  31. ↑ Ibid
  32. ↑ Ibid, Text of plate 7
  33. ↑ The Sandhurst wargame was fictionalised in Richard Cox (ed.), Operation Sea Lion (London: Thornton Cox, 1974. ISBN 0-902726-17-X). An analysis by F-K von Plehwe, "Operation Sea Lion 1940", was published in the Journal of the Royal United Services Institution, March, 1973.
  34. ↑ 34.0 34.1 Rich, Norman (1974). Hitler's War Aims vol. II, p. 397
  35. ↑ Kieser, p.251
  36. ↑ Kieser, p.247
  37. ↑ Kieser, p.249
  38. ↑ Kieser, p.251-252
  39. ↑ http://uk-tv-guide.com/pick-of-the-day/16-July-2009/documentary-britains-nazi-king-revealed
  40. ↑ http://demand.five.tv/Episode.aspx?episodeBaseName=C5143070001
  41. ↑ Rich (1974), p. 398
  42. ↑ http://books.google.com/books?id=ZKNdxlzG6okC&pg=PA62&lpg=PA62&dq=a+tv+executive+in++nazi+occupied+britain&source=bl&ots=koE6MlMAa9&sig=kOCspbsJ2-is0bP-faBkquInXfc&hl=en&ei=4smaSr7pBKONjAe1j8yyBQ&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=&f=false
  43. ↑ When Hitler Invaded Britain (2004) (TV)
  44. ↑ Hitler's Britain (2002) (TV)

Bibliography

External links