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Did the US Consider NOT Using the Atomic Bombs? & The Operation Sea Lion Fantasy | WW2 Brain Bucket

WW2 historian Paul K. DiCostanzo explores if the US ever considered not using the Atomic bomb, and why Operation Sea Lion never occurred.



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Operation Sea Lion Map 2

Outline of the never attempted Operation Sea Lion, the proposed invasion of the British Isles by Nazi Germany – September 1940


“Why didn’t Germany follow through with Operation Sea Lion and invade Britain? The British were completely exposed, and it seems like it would have made a lot of sense at the time.” – Jordan, Edinburgh

This question pervades historical quandary far and wide. The first question you must address is did Nazi Germany have the resources to invade the British isles in 1940? Better known as Operation Sea Lion (German: Unternehmen Seelöwe). 

As devastating as May and June 1940 was for the French and British, Germany had an incomplete set of strategic means to fight the kind of war an amphibious invasion of Britain required. Nor did Hitler have the fundamental political inclination for such a fight, which is where answering this question begins.

Hitler, the British & the War He Never Wanted With Them

Hitler in his infamous political manifesto Mein Kampf spoke very highly of the British and their global empire at the time of its writing. Hitler saw the British as racially kindred to his so-called Aryan race, and admired their acquisitive track record over the past 500 years – especially in India.


Hitler in the early years of his rule embarked on a major diplomatic initiative to establish a formal alliance with the British. Hitler’s envisaged alliance sought to achieve two primary aims:  

Establishing recognition of German hegemony over Eastern Europe, perfectly complimented by the British command of the seas and their foreign colonies. In Hitler’s view neither Nazi Germany nor the British could command both arenas, seeing the desired co-operation as a natural and realistic arrangement.

Recruiting a chief ally in his great self-acclaimed providential purpose, the destruction of the Soviet Union, and creation of German “Liebensraum” in Eastern Europe and Eurasia.

Hitler abjectly failed on both accounts, however his ambivalence for war with the British Empire persisted. The grand strategic assessment by Hitler was that Germany had historically been a continental power, and he planned his course of action for conquest accordingly.

Moreover that ambivalence for military conflict with the British lead to Germany never seriously preparing for a war that would include the mammoth task of invading the British Isles. It would later have immense consequences for Germany prosecuting the war.


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With France’s stunning collapse in June 1940, and the resulting German hegemony on the continent left it in a position Hitler did not seriously anticipate: British obstinance in continuing the war. 

Hitler viewed the war as effectively over at the end of June 1940, which for all practical purposes it was given no British forces were then fighting on the continent itself. Hitler thought that with the fighting in Europe at its conclusion, the British would certainly make the practical decision to come to terms with Germany, formally ending the war. It did not.

With this in mind, exactly what would have German forces needed to accomplish to successfully invade Britain in Operation Sea Lion?

The Minimum Requirements for Germany to Successfully Invade Britain in Operation Sea Lion

For Germany to cross the English Channel, a feat too great for even Napoleon a century prior, it was necessary to fulfill several main objectives to give such an assault a plausible probability for success. The following are some of the major prerequisites for Operation Sea Lion:

Achieve air supremacy over the skies of southern England by crippling the RAF, simultaneously protecting the invasion beaches, and facilitating the bombing of critical inland targets.


Secure the easternmost and westernmost approaches to the English Channel, thwarting the British Homefleet from heavily damaging – if not annihilating – incoming invasion waves and logistical support.

Ensuring the continuous flow of troops, armor, heavy weapons platforms, fuel, and general supplies to the invasion beaches.

Successfully gaining footholds on the southern English invasion beaches, and breaking out inland.

• Utilizing the extremely limited window in September 1940 that presents the most favorable weather conditions required for crossing the notoriously temperamental English Channel.

The aerial campaign known as the Battle of Britain was the foremost step to enact any possible invasion of Britain in 1940. The British Royal Airforce’s (RAF) victory during the battle, while genuinely tremendous, has fallen into the popular fallacy that it prevented the invasion of Britain.


Germany certainly required air supremacy to have any chance for a successful invasion of Britain, it is true. The Luftwaffe’s failure to do so however was far from the sole reason Sea Lion was stillborn upon original conception. 

So with these qualifications for invasion in mind, what was Hitler to do with the last major enemy belligerent in his war. Realistically, Germany had limited means to force the peace Hitler desired. Germany’s limitations for Sea Lion were none more pronounced than its surface blue water naval capabilities. 

Nazi Germany on the High Seas

For all intents and purposes, Germany went to war several years too early to seriously challenge the British or French in naval surface warfare. Unlike the formidable Imperial German High Seas Fleet during the Great War, Nazi Germany did not possess nearly the same numbers in their surface naval forces. Moreover, despite all of their military misfortunes fighting on the continent itself in 1940, Britain was still the world’s foremost naval superpower. 

Plan-Z was the Kriegsmarine’s – German Navy – construction plan to create a blue-water rival of the Royal Navy. The caveat to their plans however was that it was not projected for completion until 1943 at the earliest, four years after Hitler plunged Europe into war.

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The lack of a formidable surface naval presence made any cross channel operations invading Britain from northern France or Belgium dubious, as Germany could not challenge the onslaught of the formidable British Homefleet. 


The Royal Navy’s Homefleet was stationed at Scapa Flow in Scotland, and was chosen as the best area to coordinate and execute the naval blockade of Germany as was also conducted in the First World War. In case of an invasion, the Homefleet could have responded to any cross channel invasion within a day – entirely outclassing their invading enemy, and unceremoniously halting Sea Lion in its tracks.

Nor did Germany have anything approaching adequate purpose built landing craft; similar in nature to the Allied Higgins boats (LCVP) deployed later in the war, that would be indispensable for undertaking any variation of Sea Lion.

When Operation Sea Lion was hastily being planned and assembled following the defeat of France in June 1940, Germany appropriated continental riverboats, various barges, small commercial fishing vessels and tugs intending to create ersatz invasion landing craft. Theirs was a paltry attempt for overcoming their lack of strategic capabilities for undertaking their amphibious assault in Operation Sea Lion.

With a lack of purpose built landing craft, the Germans couldn’t reliably ferry its forces to the beaches. Additionally, the Kriegsmarine’s wanting surface vessel presence couldn’t protect the sea lanes to the invasion beaches located in southern England. Therefore they would not have been able to sustain the logistical and reinforcement support any invasion force requires – if they managed to land forces at all.

“[l]ogistics is the ball and chain of armored warfare” – General Heinz Guderian

Heinz Guderian, one of the key figures in developing German combined arms warfare doctrine – “Blitzkrieg” – once stated, “[L]ogistics is the ball and chain of armored warfare.” His military planning truism was front and center in any conception of Sea Lion, as invasion forces would require the continuous replenishment of all the materials necessary to continue fighting without interruption. 


To further compensate for German naval inferiority vis-à-vis the Royal Navy, the Luftwaffe was saddled with bombing British vessels to help prevent their breaking into the Channel invasion lanes, and running roughshod.

During the Dunkirk evacuation, the Luftwaffe sank six British destroyers and 200 crafts overall. Though attempting to sink Royal Navy vessels at sea poised for combat, that were not simultaneously occupied with a major evacuation was a different prospect entirely. Nor were they orders to be relished by even the most gung-ho Luftwaffe pilot. It was but another element in striving to compensate for Germany’s naval deficiencies.

Overall, the dearth of proper resources for such an attempt blatantly belies the fact that Hitler never seriously considered invading and occupying the United Kingdom.

Germany’s lack of adequate naval presence would have been a trump card. Nor was the Wehrmacht itself designed with an amphibious invasion the likes of Sea Lion in mind.

Hitler still possessed that same continental view of German power, at least by that juncture in the war, and crossing the English Channel was not something the Wehrmacht was either trained or equipped for in the least. Moreover, there was significant internal discord over the specifics of Operation Sea Lion itself.


Wehrmacht vs. Kriegsmarine: Fighting the Allies and Each Other

When it came to planning Sea Lion at the proverbial map table, the Kriegemarine and Wehrmacht had serious disagreements. Both parties did not see eye-to-eye on the best way to invade Britain.

The Wehrmacht envisaged Sea Lion occurring on a broad front, stretching from Dover to Lyme Regis. The first and second wave of invasion forces coming ashore were comprised of

 6 infantry divisions

 1 specialized Mountain division

 1 SS motorized regiment


 Motorized Großdeutchland regiment

 2 Panzer divisions

 1 division of Fallschirmjäger (Paratroopers) covering both the westernmost and easternmost flanks of the invasion force.

The entirety of Sea Lion’s initial assault wave was to include a landing totaling 67,000 men. Sea Lion therefore was composed of a little more than one-third of D-Day’s initial phase of landing forces.

The Kriegsmarine conversely insisted on an invasion over a more narrow front, based on its limited naval assets being unable to support an invasion of the Wehrmacht’s proposed scope.


In discussing Operation Sea Lion, the perennial elephant in the room is how it stacks up against later Operation Overlord. As both sought to achieve the same aim, albeit in opposite directions, it is an unavoidable comparison.

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Operation Sea Lion vs. Operation Overlord

The best method to weigh this scenario is by comparing Operation Sea Lion to the Allied qualifications for launching Operation Overlord, or D-Day in June 1944. 

Qualifications for Launching D-Day:

 Achieving air superiority by defeating the Luftwaffe, and ensuring the Allies firm control over the skies of Western Europe.

Prevail in the Battle of the Atlantic, allowing the vital transatlantic supply lines to function unimpeded from U-Boat raids, thus ensuring the operational artery indispensable to support the cross-channel invasion.


 Through the auspices of Operation Bolero beginning in early 1942, the continuous staging of US Army divisions, military equipment and supplies in Great Britain over two years for the eventual expected Allied invasion of northwest Europe. 

 Accumulating overwhelming naval support to ferry, protect and support the invasion forces landing on the beaches of Normandy. The specific tasks included, but were not limited to, providing continual logistical support, medical support, providing artillery bombardment and ensure cover over the invasion beaches. 

 Design, manufacture and deploy the necessary Higgins boat (LCVP) landing craft – always seemingly in short supply – to safely ferry combat units to the beach. In addition to constructing a formidable number of Liberty ships to ferry the invasions heavy equipment, armor, and related equipment for both the initial landing assault on Normandy, and their reinforcements. 

 Design, construct and deploy two Mulberry Harbors to facilitate refueling needs for the largely mobile Allied Expeditionary Force.

Build and deploy PLUTO – Pipeline Under the Ocean – a large pipe laid on the bed of the English Channel to send patroleum to France that was 130km (or 70nMi). 


Training the Allied armies for many months to handle the unique challenges of amphibious invasion, as well as the expected carnage that fight would require. (Note: The U.S. Marine Corps – the branch uniquely qualified to conduct amphibious assaults – were largely absent from D-Day, being mostly deployed in the Pacific)

These are but a few of the major points of strategic necessity to make the invasion of Western Europe across the English Channel possible, and the Germans possessed almost none of those abilities in 1940 for Sea Lion.

“On land, I’m a hero. On land, I’m a coward.” – Adolf Hitler

According to German general Franz Halder, head of the OKH in his personal diaries, Hitler spoke to his inner circle about making a peace “She [Britain] felt honorable.” Hitler and his admiration for the British is well documented, but these sentiments were also the product of the fact Hitler was neither seriously interested in invading Britain, and recognizing the absence of that possibility. According to Halder’s diaries Hitler famously stated, “On land, I’m a hero. On water, I’m a coward.”

There are a great many factors that went into this equation, and there is every reason to believe that such an invasion as Operation Sea Lion would have been a disaster.

Churchill, in the estimation of his co-biographers William Manchester and Paul Reid in The Last Lion: Defender of the Realm 1940-1945, never seriously believed that a German invasion was a realistic possibility, recognizing Germany had no bridge across the sea.


Churchill as a wartime PM sought to ensuring the best preparation possible at home should it happen beyond all expectations, in addition to keeping British minds and hearts focused on the long term objective of winning the war.

In total this casts the eventual alternative to Operation Sea Lion Hitler chose to challenge the British further, the Blitz, in a new light. 

Hitler’s Inadequate Alternative to Operation Sea Lion & His Greater Ambitions

Hitler in late 1940 was faced with the strategic reality of an inability to achieve a peace with Britain, or invade the British isles, ultimately settled on the subsequent Blitz.

As incredibly destructive as the Luftwaffe nighttime bombing campaign was in Britain through the end of 1940 and early 1941, it was a strategic contingency plan; the purpose of the Blitz aimed to break British domestic morale and force a change in government. Presumably that successor government would agree to the accommodation Hitler sought.

The Blitz not only failed to break the resistance of the populace, it had the opposite effect by making the British people more implacable in their will to continue the war against Germany.

The Blitz without question was not an act of German military superiority, but a demonstration of the limits of German power and capabilities – serving as less than a half-measure to defeat Britain. Moreover, it was also surely the result of Hitler’s much grander ambitions growing in the East.

The Seeds of Barbarossa

As the fall of 1940 came and went after defeat in the skies of Britain, lacking a bridge across the sea to follow through with Operation Sea Lion, with no prospect of peace with the British, Hitler’s true focus shifted east over the European map. Hitler thought it time to begin preparations for invading the Soviet Union. Hitler proceeded to issue Führer Directive No. 21 in December 1940 – that would culminate with Operation Barbarossa in June, 1941.

Now you know the rest of the story.

Do you have a question you want to answer about WW2? Email the Brain Bucket!

Suggested Reading:

“The Storm of War: A New History of the Second World War” by Andrew Roberts

“The Last Lion: Defender of the Realm 1940-1945” by William Manchester & Paul Reid

“The Second World Wars: How the First Global Conflict was Fought and Won” by Victor David Hanson

“The Battle of Britain: Five Months that Changed History May-October 1940” by James Holland

Recommended Viewing:

“Hitler and the Invasion of Britain” (1998), BBC Timewatch

Write to Paul K. DiCostanzo at

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Paul K. DiCostanzo is the Managing Editor for TGNR. He is a noted public speaker, an emerging historian of the Second World War, a vocal advocate for Crohn’s Disease/Ulcerative Colitis, and highly regarded interviewer. Paul K. DiCostanzo is Co-Host for the A.D. History Podcast. The A.D. History Podcast explores world history of the last 2000 years in an unprecedented fashion; with each episode covering a 10 year period beginning in 1AD, until reaching the present day. Ultimately finding the forgotten, as well as overlooked threads of history, and weaving a tapestry of true world history. Paul is author of the reader submitted Q&A column: WW2 Brain Bucket. The Brain Bucket answers readers submitted questions on all things regarding the Second World War. Paul has served as Managing Editor for TGNR since March 2015. Prior to TGNR, Paul has a background in American National Security and American Foreign Policy.