Operation “Sea Lion” Invading England In 1940? [Part Five]

December 5, 2016 by crew

Well, we’ve drawn up the plans, we’ve weighed the options, we’ve thrown the dice, and now the time has come for us to bring our explorations of “Operation Sea Lion” to an end. Could the Germans really have attempted an invasion of Great Britain in 1940? What would that invasion have looked like? Did they really have a chance?


It’s been quite a journey. Part One gave us an overview of the project. Part Two saw the Germans open their invasion. In Part Three they expanded their beachhead and the British launched their first counterattacks. In Part Four came the climax and final outcome, or at least one possible outcome.

But now we can look back at what we’ve examined so far and really take a deeper dive into Sea Lion’s prospects. What were the Germans’ chances, really? What other plans and time frames can be examined? If the Germans would have failed, WHY? Conversely, HOW could they have won? What factors really would’ve made a difference?

The Case For Seelöwe

So we’ve already established (at length) the prerequisite that for Sea Lion to any chance at all, the Germans must win the Battle of Britain. In fact, it was precisely the Germans’ failure to do this that compelled them to cancel Sea Lion.


But if the Germans win the skies, what then? Let’s take a fresh look at some potentially misunderstood factors.

The British Forces

One thing that should be kept in mind is just how weak the British Army was at the time. The B.E.F. represented some 70% of the British Army, and the B.E.F. had just suffered a catastrophic defeat that had cost them virtually all real war-fighting equipment.

On the other hand, other non-British Commonwealth units like the New Zealand and Canadian Divisions were deployed in Britain and would have helped in the defence. However, it seems that other units like 7th Armoured, 6th Australian, and 4th Indian Divisions could not have been brought back to England in time to face an invasion in 1940.


With the British it’s not a shortfall of manpower, and certainly not courage. It’s equipment and preparation. Many World War II campaigns demonstrate that vast reserves of manpower don’t help if you don’t have the right vehicles, heavy weapons, munition stockpiles, training, doctrine, all of which the British were desperately short on in 1940.

The German Forces

The Germans are also somewhat ragged after the Battle of France. However, because Operation Sea Lion would have been smaller than Case Yellow or Case Red, it’s easy to imagine that some German divisions and corps could have been “condensed” into the required fully-manned and equipped invasion divisions in September of 1940.

For instance, the nine or ten panzer divisions in the French invasion could have contributed to rebuilding the four that would have participated in Sea Lion. Despite combat losses and maintenance problems, it seems and Rundstedt’s Army Group A could have been ready to launch a real invasion in very short order.


This presumption breaks down, however, when it comes to airborne forces. One can’t just “transfer” infantry to the paratroopers without weeks of training, to say nothing of transports, gliders, etc. A lot was expected of airborne forces in Sea Lion, and frankly the plan has glaring holes where there just aren’t enough of these elite troops.

The Royal Navy

The British Royal Navy is probably the most overestimated factor in Sea Lion. Often seen as a tremendous obstacle to any attempt to cross the Channel, the fact is that the Home Fleet only had one carrier and five battleships / battlecruisers in the fall of 1940, all of them at least 25 years old.

Furthermore, German aircraft and submarines showed that they were very capable of sinking these assets. The Home Fleet was hopelessly over-prepared for the past war, and honestly couldn’t keep Great Britain FED without massive support from the United States which was not forthcoming in the summer of 1940.


All that said, while the Royal Navy seems incapable of stopping an initial invasion, they could have easily strangled said invasion once the weather started grounding the Luftwaffe in October and November. British dreadnoughts do not need sunny skies to sink German transport ships, after all.

Disunity Of Command

Without a doubt one of the worst obstacles to Sea Lion was presented by the Germans themselves. Simply put, there was no unity in the higher levels of German command. Throughout the war, bad liaisons, miscommunication, poor coordination, and outright rivalry plagued German planning and operations, costing them many battles.

Although the OKW (Oberkommando der Wehrmacht - Supreme Command of the Armed Forces) technically had command over the Army, Navy, and Air Force, they really didn’t. Also, the OKW didn’t have a singular head, like Eisenhower would be over SHAEF (Supreme Headquarters Allied Expeditionary Forces) later in the war.


Like many dictators, Hitler often kept authority deliberately divided between rival organisations so any real power rested ultimately with him. Indeed, only Hitler could command the Army, Navy, and Air Force with the coordination required by an operation like Sea Lion. But when a rank amateur like Hitler is your military commander …

German Victory Conditions

So if the Germans were going to succeed in Operation Sea Lion, what kinds of things would have to happen? If such a victory were possible, what would it have looked like?

We’ve already stated the Germans have to win the Battle of Britain. Taking an honest, unemotional, and unprejudiced look at the state of the British Army and the Royal Navy in 1940, it’s clear that the only think saving England from invasion was the Royal Air Force, which of course is precisely what happened historically.


Assuming the Germans could cripple the RAF in the short term (they couldn’t have done it permanently because of the range of German fighters and RAF bases in Wales and Scotland), it’s pretty clear that landings were possible. However, landing troops in Sussex and Kent, and conquering Great Britain, are two very different things.

Let’s start from a simple assumption: Germans always have to win QUICKLY. All their great victories, from the Franco-Prussian War of 1871 to Manstein’s “Backhand Blow” in 1943, all are won very fast. Germany is the boxer that HAS to knock you out in the first two or three rounds. If you’re still standing in round four, you’ve won.

So could the Germans have broken out of their beachheads in Sussex and Kent? Honestly, I believe they could have. It’s when they reach London and the line of the Thames that things get very difficult. London would have been a bloodbath, a “Stalingrad West,” not terror-bombed into surrender Warsaw or Rotterdam or left open like Paris.


Also, keeping Sea Lion supplied over the English Channel, through a long and expanding campaign, becomes unlikely. As said above, once the weather grounds the Luftwaffe, the Royal Navy can now come back into the English Channel and start sinking German supply convoys. The Germans must win well before that.

The Politics Of Sea Lion

Any real chance of German victory seems reliant on some kind of political collapse or disintegration of morale. This seems remote but it IS possible, given our scenario of a German victory in the Battle of Britain. The Battle of Britain is what made Churchill an icon of resistance, but if the Germans win that battle, he’s still “Mr. Gallipoli.”

Please bear in mind that Winston Churchill only became Prime Minister on May 10, and was far from a universal choice. Foreign Minister Halifax was still a major opponent who may have favoured a negotiated peace along with others in Parliament. Many saw Churchill’s defiance as foolhardy in the face of constant German victories.


Historically, Churchill needed Neville Chamberlain of all people to help hold his coalition together through the summer of 1940, and that was while WINNING the Battle of Britain. A German victory over the RAF, followed by successful landings, just might have ousted Churchill when the British government felt forced to offer peace.


Having considered all these factors, where are we left with Sea Lion? Honestly, once we assume a Luftwaffe victory in the Battle of Britain, a successful German landing on British shores becomes (in my opinion) surprisingly feasible.

Like all German campaigns, however, the crushing factor is time. If the Germans can win quickly, there is very little they can’t accomplish. If their landings proved successful, the shock (combined with the presumed crippling of the RAF) just might have caused a crisis of confidence in the British government. If this happens, the Germans can win.


If, however, the Germans can be contained, even for a short while, exponentially-increasing difficulties in logistics, supply, reinforcement, and shipping spin rapidly out of control. Once the weather deteriorates to the point where the Luftwaffe cannot suppress the British Home Fleet, Sea Lion is doomed.

Thank You!

This concludes our article series on Operation Sea Lion. By no means does this have to be the end of the conversation, however. Comments or questions below are certainly welcome, as well as in the Sea Lion thread we now have going in the Historical Gaming forum.

As always, I would like to thank the beasts of war team, especially @warzan for letting me publish, @brennon for being such a great editor, and @lancorz for the amazing support graphics and layout work. Also, I’d like to thank @dignity and @johnlyons for the great Weekender interview.

Most of all, however, I’d like to thank the community members who took time to read through the articles, especially those who supported the progress of the series through their many insightful comments. Community interaction is what I t’s always about, and we wouldn’t still be doing these articles without you.

By James Johnson

If you would like to write for Beasts of War then please contact us at [email protected] for more information.

"The B.E.F. represented some 70% of the British Army, and the B.E.F. had just suffered a catastrophic defeat..."

"Without a doubt one of the worst obstacles to Sea Lion was presented by the Germans themselves. Simply put, there was no unity in the higher levels of German command..."

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