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World War II: Operation Sealion

James is an online writer from Birmingham who has a keen interest in ancient history. He enjoys sharing his research with his readers.

Hitler Conquers France

Top left: German Panzers passing through a French town. Top right: German soldiers marching past the Arc de Triomphe after capturing Paris. Middle left: French soldiers on the Maginot Line. Bottom left: Allied POW's. Bottom right: French tanks.

Top left: German Panzers passing through a French town. Top right: German soldiers marching past the Arc de Triomphe after capturing Paris. Middle left: French soldiers on the Maginot Line. Bottom left: Allied POW's. Bottom right: French tanks.

Historical Background

By the end of June 1940, there were only two countries left to fall to the Germans in Western Europe. Firstly, there was Switzerland, the epitome of neutralism. The Germans were clearly interested in Switzerland but doubt existed whether it offered more as a conquered prize or as a neutral neighbour. Britain however, presented a more prestigious prize to Hitler, but also presented the greatest danger at the time to his grand plans for total domination. Britain was equipped with an industrial base completely out of proportion to its size and the resources of a world empire, both in terms of manpower and supplies.

Moreover, it possessed a formidable tradition of waging war by land and particularly by sea; most people living at that time still remembered the time when Britain truly ruled the waves. But now in the summer of 1940, Britain stood seemingly shocked and bewildered by the events of the previous couple of months in the Low Countries and France. Hitler’s Wehrmacht had swept across Western Europe in just a matter of weeks; they had trounced the British Expeditionary Force (BEF) so utterly and profoundly that there was widespread shock and disbelief that they were allowed to survive. Operation Sickle Cut had cut the British off so swiftly that the Commander if II Corps, General Alan Brooke is on record saying ‘Nothing but a miracle can save the BEF now.’

A Miracle at the Beaches of Dunkirk

British troops embarking a lifeboat at Dunkirk.

British troops embarking a lifeboat at Dunkirk.

Somehow Brooke got his miracle, or at least a miracle of some sort; More than a quarter of a million Allied soldiers were evacuated from the beaches of Dunkirk between the 26th May and the 4th June. In failing to eliminate these fighting men, the Germans committed a grave error. In the long run, it would prove to be a fatal error that would come back to haunt them. However, it’s important to remember that at the time the Germans would have regarded Britain’s land forces with contempt and irrelevance. It was easier for the Fuhrer to overlook them.

But while Hitler had good reason to write off the British Army; his failure to take into account the evacuations morale raising power is virtually inexcusable. Even to this day, we Britons still speak of the Dunkirk spirit. My granddad was one of the 300,000 or so troops extricated from the beaches and would always recall his experiences with a sort of solemn pride, before going misty-eyed as he recalled a fallen comrade or two.

The BEF’s evacuation had been led by the Royal Navy but probably wouldn’t have been possible without the assistance of the ‘little ships.’ These included ferries, fishing boats, tugs, and even sailing yachts and cabin cruisers, which all helped carry soldiers to safety. Amazingly, all of these ‘little ships’ were manned entirely by their civilian volunteers. The excitement of the experience produced a national adrenaline surge; the Brits were exhilarated by the skin-of-the-teeth heroics witnessed on the beaches of Dunkirk.

An Amphibious Invasion

Hitler’s plans for Operation Sealion, as recorded in his Directive No. 16 were issued on the 16th July. In it he stated:

Since Britain shows no sign of being prepared to come to an agreement despite her desperate military situation. I have resolved to prepare- and, should it be necessary, pursue- an amphibious operation against England.

The point of this operation will be to prevent the English homeland from being used as a base for the continuation of the war against Germany. If need be, the whole island might be occupied.’

The amphibious force referred to was to move along a 'broad front' stretching from Ramsgate to the Isle of Wight. This far from the continent, the Luftwaffe would have to provide a substitute for artillery, while the navy would have to take on the role of engineers. This is what Hitler thought at least, he also stated that all of the different branches of the German military should think things through from their own perspectives. If any advance operations such as the occupation of the Isle of Wight or Cornwall, were going to be needed to make the landing possible, then this was the time to plan them. Though of course, the final decision to proceed lay with him.

The start of Hitler’s Directive states ‘Since Britain shows no sign of being able to come to an agreement...’ An interesting way to start an invasion directive against your sole remaining enemy; was there perhaps a hint of wistfulness in the Fuhrer’s tone? Had Hitler been hoping that Britain would rethink their position and spare themselves further bloodshed?

That almost certainly seems to be the case when he made the ‘Last Appeal to Reason’ in the Reichstag on the 19th July 1940. Copies of Hitler’s transcript were showered right across south-eastern England from German planes. The Nazis, he insisted had only ever wanted to free Germany from the unjust penalties laid upon it by the Versailles Treaty and also from the ‘fetters of a small substratum of Jewish-capitalist and pluto-democratic profiteers. Surely right-thinking Englishmen and women would see justice in this fight.

While it would be incorrect to describe Hitler as an Anglophile, he was a big admirer of the British imperial achievement. Even while the Battle of France raged relentlessly, he spoke in flattering terms about the ‘civilisation’ that Britain had given to the world. All in all, the formulation and nature of Operation Sealion seemed a bit slap-dashed and rushed; but why? Well, the truth was that Hitler’s heart just wasn’t it and ultimately that proved to be one of the biggest reasons why firstly the BEF were allowed to escape and why ultimately the Sealion failed to swim.

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The Invasion Plan

The German invasion plan shows that their primary objective was securing the Kent and Hampshire coast before striking north towards London.

The German invasion plan shows that their primary objective was securing the Kent and Hampshire coast before striking north towards London.

Preparations and Dilemmas

Hitler ordered that preparations had to be completed by the middle of August, so basically he gave his senior officers four weeks to get everything into order. In that time, the Fuhrer noted, that certain key conditions had to be met:

  • The RAF had to be neutralised, both physically and in morale. Hitler needed assurances that it would be unable to put up any significant resistance to the German invasion
  • All sea lanes had to be cleared.
  • The entrances to the Straits of Dover and the western approach to the Channel in a line running from Alderney to Portland had to be closed off by minefields.
  • The landing zones had to be covered by heavy artillery on the continental coast.
  • The British naval forces had to be kept occupied both in the North Sea and by the Italians in the Mediterranean for the period before the invasion.

All of these conditions boiled down to the same thing; the English Channel effectively had to become some sort of German pond, a place where vast numbers of troops could simply make their way across easily and safely. The shores too had to be under German control.

These conditions were all the more important because the Germans didn't have any purpose built landing craft to call upon. Hitler hoped to do the whole thing using canal and river barges. Of the two thousand or so craft his Kreigsmarine had managed to commandeer in Germany and the occupied countries, only a third were engine powered, and those engines were designed for use in sheltered inland waterways only. The remainder would have to be towed across the Channel by tugs and other powered sea vehicles. Moreover, when they finally reached their destination, they would have to be painstakingly manoeuvred into position so that the troops on board could disembark safely. Also, the tanks, trucks, heavy equipment, and other materials needed to be unloaded without loss. These are not the kind of manoeuvres that one can achieve under heavy fire or in heavy seas. It may seem that Operation Sealion failed due to impracticality, but it might have worked had the right conditions prevailed at the time.

The difficulties facing the operation had been identified as early as 1939 when army chiefs drew up their own plans for an amphibious invasion of England in the study document Nordwest. They identified Belgium as the starting pointing point, with the landing site much further north, along the East Anglian coast. But these preliminary plans received a scornful rejection from Herman Goring. The Reichsmarschall was so pessimistic about the prospect of any invasion that he said it ‘could only be the final conclusion of an already victorious war with Britain.’ Any resistance met would be too much, he felt for what was bound to be a slow and cumbersome and mostly defenceless invasion force.

The Landing Craft

German invasion barges assembled in the German port town of Wilhelmshaven.

German invasion barges assembled in the German port town of Wilhelmshaven.

German Firepower

Despite a certain degree of pessimism among the German high command, it should be noted that circumstances actually favoured the Germans. They had complete control of the Pas de Calais coast in northern France, so it was easy enough to bring up big guns that could pound British ships in the Channel, and even to some extent the southern English coast. The largest of these formidable guns, the K12 had an 8-inch barrel and a range of 71 miles, meaning that even from the Pas de Calais, the Germans could conceivably shell London. There were four permanent batteries, fortified with concrete, that were placed in positions that ensured that every square inch of the Channel was covered. The Germans also brought several mobile batteries into play, meaning that they were able to pick off any British vessels more or less at their own will. More mobile batteries were made ready for installation on the English coast just as soon as a successful landing had taken place.

The ‘broad front’ originally earmarked for landing was quickly narrowed; landing men in meaningful numbers along some 120 miles of coast would have required a force of over 160,000. So it was decided that the landing area would extend from Rottingdean, just east of Brighton, to Hythe, in southern Kent. Even this relatively short area would still require a force of some 67,000 troops.

The Kreigsmarine would provide an escort, but the emphasis would be on creating diversions in the days before the attack took place. For all the ferocity of its U-boat war, Germany’s surface navy was small and weak. Particularly in comparison with that of an island nation that, despite its beleaguered state was still strong. Britain could still boast that it ruled most of the waves, and had done so virtually unopposed for two centuries. There was nothing to be gained from taking on the Royal Navy in a straight fight. So it was hoped that the diversionary sorties to be carried out by the cruiser Admiral Hipper in the Atlantic between Iceland and the Faroe islands would effectively draw away British naval vessels.

The Few

Many of the pilots flying for Britain came from occupied countries. This photo shows the men of the 303 squadron, all Polish, who had managed to escape Nazi occupation.

Many of the pilots flying for Britain came from occupied countries. This photo shows the men of the 303 squadron, all Polish, who had managed to escape Nazi occupation.

Foiled by the Few

Hitler can at least be commended on having spotted the main weakness of his own scheme; the RAF needed to be neutralised at least, preferably destroyed. In the event, those brave men, that Churchill would later call the ‘Few’ took to the air in July 1940 in response to wave after relentless wave of German attacks. The Battle of Britain would decide whether the land of Shakespeare, Newton, and Darwin would remain a free country.

Several weeks later, the Luftwaffe, the key component to the success of Operation Sealion had been driven from the English skies. Britain had saved itself from invasion and gained precious time. The rest is, as they usually say history. Operation Sealion retreated to the confines of historical what-ifs, and in late September, Hitler officially dropped the operation, in a rather quiet and hushed-up way.


Venkatachari M from Hyderabad, India on November 23, 2015:

Much informative article.

Kristen Howe from Northeast Ohio on November 23, 2015:

JKenny, this was an interesting hub about the 2nd world war and how operation sea lion worked between Hitler and Churchill, when it became success. Excellent read to learn more about this pivotal part of our US history in wars. Congrats on HOTD!

Hunter Denomme on May 27, 2014:

Germany never took Britain after 57 nights of bombing on London Hitler turned his back on England and invade USSR witch cost him the war and Winston Churchill died in 1965 not during the war. Haft of this is wrong and needs to be fixed

James Kenny (author) from Birmingham, England on December 23, 2012:

Yes I think you're right BC; also, the Dunkirk evacuation played a major role too, as the fact that 300,000 troops managed to escape the clutches of Hitler was seen as a small victory. If Hitler hadn't have halted his troops in France then he could have easily wiped out the BEF.

BC on December 22, 2012:

I really think Churchill played a large part in Britains victory, I believe he truly gave some of the best speeches I've heard and really boosted the confidence of the RAF and the British citizens

James Kenny (author) from Birmingham, England on August 25, 2012:

Thanks very much old abion, really appreciate your kind words. Thanks again.

Graham Lee from Lancashire. England. on August 25, 2012:

Hi JKenny. Brilliant and informative to say the least. Well paced and presented. Yes, allowing our escape from Dunkirk was a great mistake. Your enthusiasm and research are clear. Well done.

Voted up and all.


James Kenny (author) from Birmingham, England on August 20, 2012:

I know Suzette- its amazing to think how close we came to losing the war. I'm very grateful that in the end, everything worked out for the best, because I don't think I'd want to live in a fascist country. Thanks for popping by.

Suzette Walker from Taos, NM on August 19, 2012:

Very interesting and informative. I didn't know a lot about this invasion. I remember the blitzkrieg of London and parts of England, but didn't know about the initial invasion plans. Thank goodness it didn't work or we might all be speaking German today.

James Kenny (author) from Birmingham, England on August 18, 2012:

Indeed he was Gypsy, you can understand why even his own generals tried to assassinate him. You often get the impression that if Hitler had listened more to his generals then Germany might have won the war.

Gypsy Rose Lee from Daytona Beach, Florida on August 17, 2012:

Voted up and interesting. Thanks for this very informative and fascinating hub of a part of history which I didn't know. To me it has always seemed that Hitler was quite a bit too sure of things for his own good. Were he allowed to act as he wished things would of turned out much worse than they actually did. Passing this on.

James Kenny (author) from Birmingham, England on August 17, 2012:

Indeed they were Deb and thank god for it, because if they'd acted more sensibly then they may have eventually invaded and conquered Britain. Thanks for popping by.

Deb Hirt from Stillwater, OK on August 17, 2012:

Hitler was sadly mistaken in underestimating the power of the RAF. Also, the evacuation did wonders for morale, like you indicated. Germany was a little cocky for its own good.

James Kenny (author) from Birmingham, England on August 17, 2012:

I know, I found that hard to believe too Chris. But then again I get the impression that Hitler only attacked us because we allied ourselves to France. I remember watching a documentary that stated that Hitler hoped to forge some sort of Anglo-Saxon alliance with Britain- which may explain why he and Edward VIII were on good terms. But, I suppose when Edward abdicated that ended of any chance of an alliance. To be honest, I'm glad that we became an enemy of Nazi Germany; Hitler was a maniac and total crackpot that needed to be stopped. Thanks, as always for stopping by.

Christopher Antony Meade from Gillingham Kent. United Kingdom on August 16, 2012:

Great job James. It's hard to believe that the Germans did not have landing craft. It should be blindingly obvious that they would need them. It lends credence to the idea that Hitler, even at that late stage, still was convinced that Britain would make peace.

Thank God we did not.

James Kenny (author) from Birmingham, England on August 16, 2012:

Thanks very much teaches; strangely we never really learned about the Battle of Britain and Operation Sealion in school, which is strange considering its 'our finest hour' and something that is etched into our collective memories through talking to parents or grandparents. Thanks for popping by.

James Kenny (author) from Birmingham, England on August 16, 2012:

Thanks very much Joan, I must admit I haven't read your articles on counter espionage, so I'll get and do that asap. I really appreciate your kind words. Thanks for stopping by.

Dianna Mendez on August 16, 2012:

What a great hub post on this topic! I wish I would have had a history lesson like this when I was in school. Well done and voted up for the high interest and design.

Joan Veronica Robertson from Concepcion, Chile on August 16, 2012:

Hi Jkenny, congratulations on a very well written description of the period from Dunkirk to the end of the plans to invade Britain! Voted up, awesome and interesting. Although I was very familiar with this, your description gripped me and I read from start to finish! This coincides with the period in which my Dad was debating on his future involvement in the War, from Chile, as I have described in my articles on counter espionage in Chile, so we are writing in parallel, so to speak!

Thank you for a good read and have a good day!

James Kenny (author) from Birmingham, England on August 16, 2012:

Hi Harald- I agree, for me the turning point of the entire plan was when a German bomber plane inadvertently bombed London. If I remember correctly Britain responded by bombing Berlin- this incensed Hitler who altered his strategy from bombing airfields to bombing cities. Sealion would have definitely succeeded if they'd continued pounding airfields. Like you, I don't think the Germans would have needed to conquer the whole of Britain, once London was taken then surely even a man like Churchill would have agreed terms. Thanks very much for popping by.

David Hunt from Cedar Rapids, Iowa on August 16, 2012:

This is a very nice hub, jkenny. Operation Sealion has always been one of those great "what ifs" of history. Without Britain, America would not have been able to build up its European forces. Without Britain at his back, Hitler might have taken Moscow (they got within sight of Moscow's suburbs). As it is, in order to prepare for Operation Barbarossa, Britain was left, albeit severely wounded. Could Sea Lion have succeeded? If they hadn't diverted from fighting the RAF and started bombing cities, I think Sea Lion could have succeeded. There were still plenty of people in high places who were defeatists and the Germans wouldn't have had to immediately conquer the whole island. Anyway, that's my two cents. Voted up and interesting.

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