Operation Sealion was the name given by Hitler for the planned invasion of Great Britain in 1940. Operation Sealion was never carried out during the war as the Germans lost the Battle of Britain and it is now believed that Hitler was more interested in the forthcoming attack on Russia as opposed to invading Britain.

Göering, on right, overlooking the White Cliffs of Dover

The projected invasion on Britain included:

Army Group A (6 divisions) invading Kent via the areas near Ramsgate, Folkstone and Bexhill

Army Group A (4 divisions) invading Sussex and Hampshire via the area around Brighton and the Isle of Wight.

Army Group B (3 divisions) invading Dorset via Lyme Bay

From Kent, Army Group A would advance to south-east London and then to Malden and St. Albans north of London.

From Sussex/Hampshire, the 4 divisions of Army Group A would advance to the west of London and meet up with the other 6 divisions of Army Group A, thus encircling London. Other parts of the group would head towards Gloucester and the River Severn region.

From Dorset, Army Group B would advance to Bristol.

The whole plan relied on Germany having complete control of the English Channel, which, in turn meant that Germany had to have control of the skies so that the Royal Air Force could not attack German ships crossing the Channel. Hence victory in the Battle of Britain was an integral part of the plan.

Operation Sealion looked simple in theory. Britain should have been an easy target. The Luftwaffe was very experienced in modern warfare, the Wehrmacht had experienced astonishing success since the attack on Poland and the British had lost a vast amount of military hardware on the beaches of Dunkirk. The RAF and the Army in Britain looked weak; only the Royal Navy seemed to offer Britain some semblance of protection.

It is said that Hitler was prepared to offer Britain generous peace terms. However, on May 21st, 1940, Admiral Raeder told Hitler about a plan to invade Britain and Hitler, it is said, was taken in by the plan. If Britain had not surrendered, Hitler had planned an economic war which could have taken a long time to be effective. However, a military conquest of Britain would be swift and decisive. The military success of the German military since September 1939, seem to confirm in Hitler’s mind that an attack on a demoralised British Army would be swift.

Towards the end of June 1940, Hitler gave the order for the German military to make plans for an invasion of Britain. In fact, they were one step ahead of Hitler here as all three branches of the German military had guessed that an invasion would be needed and had already started on their own plans.

In November 1939, the German Navy had done its own report on an invasion of Britain. It was not optimistic about its success. The German Navy detailed many problems that would be experienced for either a short crossing or a long crossing. It did not state that an attempted invasion would be unsuccessful – but it was cautious.

In December 1939, the Wehrmacht had produced its own report. This favoured a surprise attack on Britain via East Anglia by 16 or 17 divisions. However, this plan needed the support of the German Navy and they believed that the Wehrmacht’s plan was untenable as the German navy would have to protect any landing fleet of the army whilst having to fight the British Navy. Raeder believed that this was an impossible task to complete successfully. The Luftwaffe pointed out that for its part, it would need good weather for the whole of the invasion if it was to do its job – and across the North Sea this could not be guaranteed. Though the Luftwaffe had experienced success in both the attacks on Poland and Western Europe, the RAF had not used its fighter force to its full capacity in the spring of 1940.

After the fall of France, the only major European power not to have fallen was Great Britain. The problems of an invasion were known to all three branches of the German military:

Control of the Channel would be needed

Control of the skies would be needed

Good weather would be needed

However, for all of the work done by the military on a projected invasion of Britain, it seems that Hitler had little enthusiasm for it. On June 17th, 1940, the navy received a communiqué that informed them that:

“With regard to the landing in Britain the Führer has not up to now expressed such an intention, as he fully appreciates the unusual difficulties of such an operation. Therefore, even at this time, no preparatory work of any kind has been carried out in the Wehrmacht High Command.”

On June 21st, 1940, the navy was told that the Army General Staff:

“Is not concerning itself with the question of England. Considers execution impossible. Does not know how the operation is to be conducted from the southern area.”

Hitler’s position was obviously crucial as without his support no invasion was possible. At the time, it is thought that he believed that Britain would sue for peace and that he could make generous peace terms with the British on the condition that they recognised Germany’s position on mainland Europe. Even during the Dunkirk evacuation, one of his generals – Blumentritt – was astonished to hear Hitler talk about the British in glowing terms.

“(Hitler spoke) with great  admiration of the British Empire, of the necessity for its existence, and of the civilisation that Britain had brought into the world.” Blumentritt

It was only when it became clear that Britain would not sign peace terms that Hitler gave his backing to an invasion. On July 2nd 1940, Hitler gave his first tentative orders regarding a possible invasion of Britain. It stated that

“a landing in England is possible, providing that air superiority can be attained and certain other necessary conditions fulfilled…..all the preparations must be made on the basis that the invasion is still only a plan, and has not yet been decided upon.” Hitler, July 2nd 1940

On July 13th, the army chiefs presented their plan – see first box above. They were so confident of success that they believed that Britain would be occupied within a month. On July 16th a directive called ‘Preparation for a landing operation against England’ was issued which stated that

“As England, in spite of her hopeless military situation, still shows no 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 mother country as a base from which the war against Germany can be continued, and, if it should be necessary, to occupy it completely.”

The code name for this operation was ‘Sea Lion’.

At a meeting with his service chiefs on July 21st, Hitler made it clear that he recognised that the plan had its dangers – especially those identified by Raeder – but he was keen to press on with the plan so that he could turn his full attention to Russia once Britain had been defeated.

Hitler wanted Sea Lion to be over by mid-September. His naval chiefs believed that any invasion could not start until mid-September! Raeder supplied a list of reasons why the invasion could not go ahead before mid-September1940  (clearance of shipping lanes of mines, getting invasion barges ready etc) and he won the support of the army. Hitler ordered that as long as Germany controlled the sky, Operation Sea Lion would go start on September 15th 1940. Therefore, the invasion depended entirely on whether Göering’s Luftwaffe could defeat the RAF. The failure of the Germans to defeat the RAF had to lead to the cancellation of Operation Sea Lion which was announced on September 17th 1940.

One of the interesting issues to come out of this episode was the inability of the three units that made up the German military to either work together or support one another. primarily, the chiefs of the army railed against Raeder while he and his chiefs criticised the plans of the army. The Luftwaffe took the view, though it was primarily Göering’s, that any success depended on the Luftwaffe conquering the skies. Another key point that came out of this episode in the war, was Hitler’s seeming refusal to listen to his military commanders and wanting things done his way. This came out of the success the military had against Poland and the nations of Western Europe – countries attacked without the overwhelming support of the military but attacked because Hitler instinctively knew that they would win – or so he believed.