"I have decided to begin to prepare for, and if necessary to carry out, an invasion of England" - Adolf Hitler, Directive No 16
German ideas for an invasion of Britain began to formulate after the election of the Nazi Party in 1933. The subject was raised by Dr Ewald Banse in his book, Germany prepare for War!, published in 1934. In this book he proposed a cross Channel invasion of the English Coast would be relatively easy if Germany held the French Channel ports of Dunkirk, Calais and Boulogne.
The first serious planning for invasion was started in 1939. The first Army plans envisaged a joint air-borne and beach landing in East Anglia, with the coastal ports of Lowestoft and Great Yarmouth to be sized by air-borne troops and landings on the open Suffolk Coast.
Right: 1939 Plan - 'Operaton Nordwest'
After the Battle of France, the German High Command expected Britain to surrender without the need for invasion. When it was clear that this was not going to be the case, preparations were made for invasion. Hitler planed for a surprise crossing on a broad front between Ramsgate and a point west of the Isle of Wight. In Directive No 16 he considered that the following preparations would have to be put in place to ensure the success of any invasion:
1. The British Air Force would have to be eliminated so it could not put up any effective resistance against the invading troops.
2. Sea routes would have to be clear of mines.
3. Both flanks of the Straight of Dover and the Western approaches to the channel (approx. from Alderney to Portland) would have to be mined so as to be impassable.
4. Heavy coastal guns to cover the entire coastal front.
5. British Naval forces in the North Sea and the Mediterranean to be pinned down (by the Italians in the latter case). British Naval Forces in the North Sea to be attacked by bombs and torpedoes at harbour and in coastal waters.
The role of the Navy was to safeguard the invasion fleet and also secure the flanks during the Channel crossing. It was also to supervise coastal guns to be installed to cover both flanks of the crossing against interference from the British Navy. Heavy AA guns were to be mounted on railway bogies with railway turntables to be used.
The role of the Air Force was to prevent British air attacks, destroy defences covering the landing beaches and reserves immediately behind them and attack all roads that could be used for enemy troop movement. Also approaching British Naval vessels were to be attacked before they could reach the embarkation and landing points.
On July 17th Halder issued a warning order announcing the intention to invade England. The 16th and 9th Armies were to make the landings on the English South coast between Folkestone and Worthing. The 6th Army was to land in the Weymouth area.
To carry out the invasion inland waterway transport was to be requisitioned and moved to the coastal embarkation ports (from Rotterdam to Caen and the Cherbourg peninsula).
On Jul 29th orders were issued to commence training. The invasion date would depend on the time required to gain air superiority, prepare the invasion fleet and weather / tide conditions. The Army was to be ready from August 25th onwards.
Above: Training for Sea Lion: Left - loading a tank onto a barge. Right - constructing the ramp of an invasion barge. These barges were not like the
purpose built landing craft used by the Allies in 1944. The ramp would have to be constructed with the barge securely tethered and under fire of
the defending troops.
Before the invasion was launched, the German Air Force was to obtain air supremacy over the Channel. The German Air Force completed its deployment for action against the United Kingdom in July. The 2nd and 3rd Air Fleet was to operate against Southern England and the Midlands from Dutch, Belgium and French aerodromes. The 5th Air Fleet was to operate from bases in Norway against the Newcastle area to pin down British air forces based in the north. The three Air Fleets totaled 1,451 bombers and 1,308 fighters. Adlerangriff (‘eagle-attack’), the commencement of air attacks, was Aug 13th. The plan was to gain air supremacy by targeting British aerodromes and RAF operational structures as well as forcing British fighter formations into operation and destroying them in the air. It was expected to gain air supremacy over Southern England in four days. The air battle was then to be continued northwards and within four weeks (by Sept 15th) it was expected the invasion could be launched without interference from air attack.
A General Directive was issued on Aug 30th setting out the aims and plan of the invasion. The aim was to eliminate Britain as a possible base for operations against Germany (by occupation if necessary).
The Army was to affect a large scale landing on the South coast, defeat British Forces and occupy London (and other areas if necessary).
The Navy was to organize the transport (the crossing of the narrow Straights of Dover was to be treated as a river crossing while the crossing of the 9th Army from Le Havre as a landing). It was also to mine the flanks of the crossing and organize heavy coastal guns to protect the flanks. Two diversions were to be made with cruisers and empty transports, one towards the English North-east coast and one towards Iceland. A pocket-battleship was to attack commerce shipping in the Atlantic to draw off some of the Royal Navy’s strength.
The Air Force was to destroy the RAF and its bases, carry out reconnaissance and the mining of South coast ports. It was also to act as support for the Army.
The final plan would see the main landing by 16th and 9th Armies (Group ‘A’) while the 6th Army (Group ‘B’) would make a secondary landing in the Weymouth area if the situation demanded. The first wave would consist of 13 divisions, scaled down from the planned 25-40 divisions as the German Navy simply had not got the resources to carry out a landing on such a broad front as originally envisaged. Moon and tide conditions would be ideal for invasion between Sept 19th-26th and accordingly the planned date for invasion was early on the 21st.
The general plan involved specialist units seizing bridgeheads then linking up to form a unified landing area. Ports were to be seized as soon as possible. This area was to be prepared for immediate defence against British counter attacks. The armour was expected to start landing on day four and after sufficient forces had been landed the German Army was to take to the offensive (expected to be on day eight). The first objective was the line Thames Estuary – hills South of London – Portsmouth. Sufficient forces were to then be built up to destroy any remaining British units, occupy London and move on to the second objective, the line Maldon (NE of London) – Severn Estuary.
The specific Army group tasks were as follows:
Group ‘A’ – 16th Army (15 Divisions): Embarkation from ports between Rotterdam to Calais and would cross in three waves. Landings to take place on a broad front between Folkestone – Hastings. Simultaneous paratroop landings to take place on the hills north of Dover. Troops to link up with the paratroops, capture Dover and the landing grounds Ramsgate-Deal. The initial bridgehead to be secured was Canterbury-Ashford-Tenterden-Etchingham. Once the bridge head was secure troops to advance on the first general objective. Once secure motorized units were to push out to cut off London from the South and West, seize the Thames crossings to prepare for the advance onto the second general objective.
9th Army (10 divisions): To land between Bexhill and Worthing. Embarkation from Le Havre and Boulogne (where troops would land East and West of Eastbourne). Paratroops to seize the hills north of Beachy Head. The initial bridgehead was to be Hadlow Down-Burgess Hill-Westwards of Storrington.
Group ‘B’ – 6th Army: It would not take part in the first landings but if the situation was favorable would embark from Cherbourg landing in the Lyme Regis area and seize Weymouth and the hills to the North. It would then move on Bristol and occupy Devon and Cornwall.
Due to the failure to force a decision in air attacks against the RAF and in revenge for bombs dropped on Berlin, the German High Command vowed to “wipe out the cities” of England. Attacks on the RAF were relaxed and air attacks on London (‘The Blitz’) commenced on Sept 7th. With air superiority over the Channel not secured and due to losses of barges and shipping by attacks by Bomber Command, the decision to postpone Sealion was made. Some of the barges were sunk at sea (either during training or to escape attacks in the ports) and German bodies washed up on the English coast gave rise to the myth of an invasion fleet actually being launched.
With the decision to invade Russia in 1941 which required the concentration of air forces and troops in preparation for the attack, the invasion of Britain was to wait until after Russia had been defeated.
Even if the RAF had been defeated, some German Naval commanders did not believe that German air supremacy would stop the Royal Navy from attacking the invasion fleet. Another high risk factor was the fact that the transport barges could only sail in calm conditions making it difficult to land following waves of troops and supplies.
Defence Plans of the United Kingdom, TNA
Ironside's Line, C Alexander, Historic Military Press, 1998
Ironside's Line, Colin Alexander, Historic Military Press, 1988
Operation Sea Lion, Peter Flemming, Simon & Schuster, 1957
Invasion Tactics, Dr W Necker, Bernards, 1944