Operation Sealion - how Britain prepared for the Nazi invasion in 1940

In early June 1940, Britain stood alone in Europe. Since the declaration of war in September 1939, the Third Reich’s armies had invaded and suppressed Poland, Norway, the low Countries (Holland and Belgium) Denmark, and finally France.

The British Expeditionary Force had withdrawn in haste from France and the Nazis dominated Europe.

There was fear, but also indignation in the country. No-one had invaded the country since William the Conqueror in 1066, and there was a disinclination to allow Hitler to re-set the clock.

As Winston Churchill, the new Prime Minister, put it, “the Battle of France is over, the Battle of Britain is about to begin.”

On the 3^rd September 1939, Britain declared war on the Third Reich.

On the 1^st September 1939, the Blitzkrieg against Poland had started. The UK and France issued ultimatums to the Nazi forces.

The 3^rd September 1939 was a Sunday, and Neville Chamberlain, the British Prime Minister, broadcast the following:

This morning the British Ambassador in Berlin handed the German Government a final note, stating that, unless we had heard from them by 11 o’clock that they were prepared at once to withdraw their troops from Poland, a state of war would exist between us.

I have to tell you now that no such undertaking has been received, and that consequently this country is at war with Germany.

After the declaration of war, as far as the British Isles were concerned, very little happened. This period was known as the "phoney war".

There were skirmishes along the fortified border between France and Germany, and the British Expeditionary Force was based in France.

The Soviet Union invaded Finland on the 30^th November 1939, and the Nazis invaded Denmark and Norway on the 9^th April 1940, and occupied both within a fortnight.

When War broke out in September 1939, Neville Chamberlain was Prime Minster. Winston Churchill was appointed First Lord of the Admiralty, and was also a member of the War Cabinet.

On the 10^th May 1940, in recognition of the fact that he had for many years seen Hitler as a threat, George VI invited Winston Churchill to Buckingham Palace, and asked him to form a government and become Prime Minster.

In his first speech to the House of Commons after becoming Prime Minister, on the 10^th May 1940, Churchill set out the truth as he saw it.

Churchill was a man whose hour had come. He had been irrelevant in politics in the 1920s and 30s, but cometh the hour, cometh the man, and Churchill became the great war leader.

Churchill offered no magic bullets, no miracle solutions, and no false hope. Instead, as he himself said on 13th May, shortly after forming his government:

I would say to the House, as I said to those who have joined this government: "I have nothing to offer but blood, toil, tears and sweat."

Perversely, this seemed to cheer the population up a bit. Someone was telling it to them as it was, and that didn't seem all bad.

Speech in the House of Commons, 13th June 1940:

...the Battle of France is over. I expect that the Battle of Britain is about to begin. Upon this battle depends the survival of Christian civilization. Upon it depends our own British life, and the long continuity of our institutions and our Empire. The whole fury and might of the enemy must very soon be turned on us.

Hitler knows that he will have to break us in this Island or lose the war. If we can stand up to him, all Europe may be freed and the life of the world may move forward into broad, sunlit uplands.

But if we fail, then the whole world, including the United States, including all that we have known and cared for, will sink into the abyss of a new Dark Age made more sinister, and perhaps more protracted, by the lights of perverted science.

Let us therefore brace ourselves to our duties, and so bear ourselves, that if the British Empire and its Commonwealth last for a thousand years, men will still say, "This was their finest hour.

And on 4th June 1940:

We shall go on to the end, we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our Island, whatever the cost may be, we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender....

On the10th May 1940, Nazi invasions of Belgium, the Netherlands and Luxembourg began. It was a typical Blitzkrieg attack, with fast advancing troops on the ground supported by large scale air forces in the skies.

France had mobilised approximately a third of French men between 20 and 44, but training had not been sufficient, and compared with the Nazi forces, the troops were extremely ill-equipped.

On 15^th May 1940, the Netherlands surrendered, although Queen Wilhelmina escaped and established an exile government in London.

By the 14^th May, the invasion of Belgium was complete. The French armed forces and politicians were stunned into sensing defeat.

As early as the 15^th May, the French Prime Minster told Winston Churchill by telephone that it was all over. Churchill flew to Paris the following day, the 16^th May, and allied troops continued to fall back through France.

On the 10^th June, Italy declared war on France and the United Kingdom.

On the 22^nd June, the new Prime Minster, Marshal Pétain, signed the Armistice in the same railway carriage in which the then powers had signed the Armistice ending the First World War in 1918. The Armistice took effect from the 25^th June 1940.

France was divided into the puppet government of Vichy France, and the occupied northern zone. By the 25^th May, most of the British Expeditionary Force was trapped in a narrow band near the coast.

After the surrender of Belgium, the Dunkirk evacuation began. 340,000 allied troops were evacuated from Dunkirk, but almost all of their tanks, heavy guns, and armed vehicles had to be left behind.

Operation Dynamo, the Dunkirk evacuation plan, was far more successful than was anticipated. The plan envisaged 45,000 men from the BEF evacuated in two days, and thought that after that 48 hours, no further evacuation would be possible.

As well as the Naval boats transporting evacuated soldiers across the Channel, a significant part of Operation Dynamo consisted of a fleet of small ships.

On the 27^th May, the British War Ministry contacted as many small boat owners, particularly fishing boats, or private yachts along the south coast, East Anglia, and the rivers, and encouraged them to set sail for France.

700 or so small private boats set out across the Channel.

Many of the boats were used as dinghies, collecting soldiers from the Dunkirk beaches, and ferrying them out to the Naval boats further out to sea. Many other boats took soldiers all the way back across the Channel.

There was a similar evacuation, Operation Aerial, between June 14^th and June 25^th, when 215,000 allied soldiers were evacuated from Cherbourg and St Malo.

The operation and evacuation was largely successful, and not conducted under such pressure as Operation Dynamo.

During the evacuation, however, the RMS Lancastria, a Cunard Atlantic Liner which had been pressed into service, was bombed by aircraft. Nearly 6,000 men died.

A ship of a similar name, also owned by Cunard, RMS Lusitania, had been sunk in the First World War. My great-great-grandmother Fannie Jane Morecroft survived that sinking, and went on to be chief stewardess on the Lancastria. Fortunately for her, she was not on the Lancastria after it was taken over by the Navy.

Invading Britain was not going to be possible in the same way as invading continental countries.

The infamous Blitzkrieg Operations, with which the Nazi forces had rolled across Europe, needed additional help to cross the 20 miles or so of the English Channel.

On 16^th July 1940, Hitler proclaimed his Directive 16 and stated,

I have decided to start to prepare for, and if necessary to carry out, the invasion of England.

The Operation Sealion was the plan for the invasion of the United Kingdom.

The German military had started to prepare Operation Sealion in early November 1939.

Anticipating the easy victories over the low countries and France, and the invasion of Poland already completed, the German forces started to prepare.

Once Hitler had issued his directive, he commanded the armed forces, “

since England, in spite of her hopeless military situation, shows few signs of being ready to compromise.....

Hitler set four conditions which needed to be met before the operation could proceed.

• The first was that the Royal Air Force (RAF) needed to be defeated, so that the German forces had air superiority.

• The second was to clear the English Channel of British mines, and to cut off the straits of Dover from the Royal Navy by laying German mines.

• The third was to populate northern, occupied France, with artillery.

• The fourth and final condition was to use the German Navy to attack the British fleets in the North Sea and the Mediterranean, in order to prevent the Navy interfering with the invasion.

Hitler hoped that the operation, and the massive build up forces on the southern side of the English Channel, would force the British authorities in suing for peace. He was not necessarily determined to defeat Britain, he merely wished to marginalise it.

The softening up operation began. The Nazis assembled a huge fleet of vessels to take the 160,000 German soldiers across the Channel.

In the early days of September 1940, British Intelligence showed a huge build up forces in the Channel ports, including Dunkirk, Calais, and Flushing. Large numbers of bombers were also moved to air fields close to the Channel and the straits of Dover.

The moon and tide cycles suggested that an invasion between September 8^th and 10^th was the most likely. On the 7^th September 1940 the Chiefs of Staff of the British Armed Forces met, and issued an alert, Cromwell, meaning that they thought invasion was about to take place at any minute.

8pm on 7^th September 1940 was a Saturday night, and the code word was misunderstood by many defence officers. Often officers thought that the Cromwell signal meant that the Germans were actually invading, and all over England in particular, and the United Kingdom in general, Army and Home Guard units donned their uniforms, grabbed their guns, and waited for the enemy to appear over the horizon.

As the Battle of France ended, the Battle of Britain began.

The Nazi Luftwaffe had more pilots, who were better trained, and included pilots who had fought before, in the Spanish Civil War and across Europe. They also had significantly more planes.

The Luftwaffe thought it would take approximately 4 days to wipe out Fighter Command in the south and south-east of England. They then intended to spend approximately 3 weeks bombing Army and Navy sites across the UK, and also as many factories producing war material as possible.

From about the 10^th July for a month,a lot of the Luftwaffe action consisted of bombing raids over the Channel. This was intended to attack ship convoys, both merchant shipping and Royal Navy vessels.

It was an extremely difficult time for the RAF, as the constant need to patrol over the Channel exhausted pilots and wore down machines.

Beginning on the 12^th August, the Luftwaffe attempted to bomb RAF radar stations and airfields. It was an intensive and viscous bombing campaign.

On the 23^rd August 1940, bombing air raids started, with raids on Birmingham, Portsmouth, and the East End of London. There were also 24 large scale attacks against airfields, and the East Church and Biggin Hill airfields suffered particularly, being bombed 7 and 4 times respectively.

The RAF was stretched almost to its absolute limit, but the Luftwaffe still failed to establish air superiority.

At the height of the Battle of Britain on 20^th August 1940, Winston Churchill gave the famous speech in which he said:

The gratitude of every home in our island, in our Empire and indeed throughout the world, except in the abodes of the guilty, goes out to the British airman who, undaunted by odds, unwearied in their constant challenge and mortal danger, are turning the tide of the World War by their prowess and by their devotion.

Never in the field of human conflict was so much owed by so many to so few.

All hearts go out to the fighter pilots, whose brilliant actions we see with our own eyes day after day.

The RAF pilots were suffering. New pilots joining the battle measured their life expectancy in weeks.

The RAF Battle of Britain pilots became known as "the few", and continue to be so known to this day.

In early September, the Blitz against civilian targets began.

On the 7^th September, 400 bombers and 600 or so fights attacked the East End of London for approximately 24 hours, targeting in particular the docks along the River Thames crucial to the import and transport of goods.

British civilian losses during the Blitz were very heavy. Between July and December 1940, nearly 60,000 British civilians were either killed or seriously injured in bombing raids.

It wasn't just London which suffered, either. Most major cities suffered repeat bombing, such as Manchester, Birmingham, and Liverpool.

Coventry was, later in the war, almost levelled by repeated bombing raids.

A large series of stop lines were built and fortified across southern England, including the anti-tank line, known as the GHQ line which went around London, across southern England to one side, and north up the centre of England towards Yorkshire.

Large numbers of pill boxes and gun emplacements were built all along the south coast, and parts of Romney Marsh, a low lying drained marsh area in Kent, were flooded and much more of it would have been flooded had the invasion taken place.

The chain home radar system had been installed in the UK before the outbreak of the Second World War, starting in 1937. Aircraft based radar capability was an absolutely crucial aspect of the defence of Britain.

• All sign posts and place names were removed. Every railway station name sign was removed, maps were banned from being sold in the shops, and anybody wandering around in an unfamiliar area would have no idea where he was going.
• In June 1940, the Ministry of Information published ‘If the invader comes, what to do, and how to do it.’ This leaflet told British civilians what to do if and when the invaders arrived.
• Half the civilian population in the counties of Kent, Suffolk and Norfolk were relocated inland.
• Occupation committees were formed in towns and villages across the UK.
• The ringing of church bells was forbidden in June 1940; for the rest of the War the ringing of Church bells was a sign that an invasion had started.

The Local Defence Volunteers were formed on the 14^th May 1940, and by the end of June 1.5 million men, mostly either too young or too old to join the regular armed forces, had enlisted.

The unit was later renamed the Home Guard.

Popular at the time in the general imagination were historical declarations of the country's independence.

My grandparents married on the easy-to-remember date, 2nd September 1939. They listened to Neville Chamberlain's radio broadcast less than 24 hours after their marriage began.

They had intended to marry later in 1939, but as the war loomed, their plans were brought forward. My grandfather was in the Royal Navy Reserves, and assumed (rightly) that he would be called up swiftly once war broke out.

My Granny recalls that both the professional theatres and local amatuer dramatic societies in the north-west of England, where she lived, reached frequently for plays and texts which recalled the nation's independence, and resisting invaders.

She reckoned that between 1939 and 1941, she attended 5 different productions of Shakespeare's Richard II, not normally the most popular of his plays, but with a roaring speech in Act II by John of Gaunt:

This royal throne of kings, this scepter'd isle,
This earth of majesty, this seat of Mars,
This other Eden, demi-paradise,
This fortress built by Nature for herself
Against infection and the hand of war,
This happy breed of men, this little world,
This precious stone set in the silver sea,
Which serves it in the office of a wall,
Or as a moat defensive to a house,
Against the envy of less happier lands,
This blessed plot, this earth, this realm, this England

Also popular at the time were recitations of Elizabeth I's speech at Tilbury, in Essex, when the Spanish Armada was trying to invade in 1588:

I know I have the body but of a weak and feeble woman; but I have the heart and stomach of a king, and of a king of England too, and think foul scorn that Parma or Spain, or any prince of Europe, should dare to invade the borders of my realm

Also popular were the old Victorian Imperialist songs, such as Rule Britannia,

Modern songs were also produced to raise the fighting spirit, such as There'll Always Be An England.

There'll always be an England,
And England shall be free
If England means as much to you
As England means to me.

On 12^th August 1940, the Luftwaffe began to bomb British radar stations, airfields scattered across south-east England, and factories making aeroplanes and components for aeroplanes. The air operations were intended to last for approximately a month, and the invasion was planned for early September 1940.

On the 17^th September 1940, at a meeting in Berlin, Reichsmarschall Göring, Field Marschal von Rundstedt, and Chancellor Hitler, agreed to postpone Operation Sealion.

Complete air superiority had not been achieved, and the operation was postponed.

Forces remained earmarked for Operation Sealion until after the Nazi invasion of Russia in February 1942, but the real threat was over by the end of 1940.