Operation Sealion: The Planned German Invasion of Britain A Primer and List of Sources

German Plans
List of Sources
Wargame Resources

Author's Note: This article is designed only as a short introduction to the topic of Operation Sealion. At some stage, the author intends to write a much more detailed series of articles about this plan, as well as the plans for British defence against such an invasion and the plans for resistance in the event of occupation.


This year (2010) marks the 70th anniversary of the Battle of Britain, the gallant struggle of the RAF's Fighter Command against the might of the German Luftwaffe.(1) While a major campaign in itself and the subject of numerous books, articles, webpages and even a major motion picture, this attempt by the Luftwaffe to attain air superiority over Great Britain by defeating the RAF, which became known as the Battle of Britain, was in fact fought as the main prerequisite for the planned German invasion of Britain, codenamed Operation SEALION and originally scheduled for September 1940. The evacuation of the BEF from Dunkirk had left the Wehrmacht in control of the Channel Coast after the fall of France and while this was an enviable position to be in, it meant that the Germans were now forced to contemplate what to do about what the Chief of Luftwaffe Intelligence called 'the most dangerous enemy'. The dire state of the British Army after the evacuation from the continent demanded immediate attention and while it would take time for reorganise and re-equip the ground forces available; they could only get stronger as time went on. Arguments still rage to this day as to how serious Hitler actually was, in contemplating an amphibious invasion of Britain, but whatever the case, the preparations that were made were conducted in a serious manner and involved a considerable cost to the German war effort. Whatever their actual chances of success, the landings were planned as a contingency and were dependent on the efforts of the Luftwaffe to achieve air superiority over the landing area and much of southern Britain, in order to forestall both the RAF and Royal Navy intervening in the operation.


Operation Sealion Figure 1: German Command Structure
Operation Sealion Figure 1: German Command Structure

OKW (Oberkommando der Wehrmacht or High Command of the Armed Forces) was the main strategy-making body and was headed by Hitler, with Generals Keitel and Jodl alongside. To this reported the high commands of the various services, the OKH (Oberkommando des Heeres - Army High Command under Generalfeldmarschall von Brauchitsch), OKM (Oberkommando der Marine - Naval High Command under Grossadmiral Raeder) and OKL (Oberkommando der Luftwaffe - Air Force High Command under Reichsmarschall Göring). See Figure 1. The timeline of events relating to Sealion is as follows:

German Plans

Operation Sealion Figure 2: German Order of Battle, mid September 1940 - Ground Forces
Operation Sealion Figure 2: German Order of Battle, mid September 1940 - Ground Forces

The main planning for the operation came out of two directives from Hitler and a supplemental one from the OKW, the first of which was issued on 16 July 1940. As mention above, up to this point, various meetings had occurred and planning documents had been issued by all three services and their High Commands, including a memo from Jodl dated 12 July 1940 which alluded to the operation being called Löwe (Lion) and being a broad front operation, not much more complex than an extended river crossing. While the Heer found the idea appealing, rivers are not tidal, are not subject to severe weather and don't have the enemy's Home Fleet in a position to contest the crossing. Following this was a meeting between Hitler, von Brauchitsch, and General der Artillerie Franz Halder (the Army Chief of Staff) on 13 July 1940, where Halder presented more detailed planning proposals that outlined an operation incorporating 39 divisions and around 500,000 men (published 20 July). Hitler authorised continued preparations but was puzzled over the lack of peace feelers from Britain, as he once again outlined that he would prefer a negotiated settlement as he did not wish to hand Britain a military defeat which would disrupt the empire and only be of benefit to Japan and the USA. Hitler also reviewed his decision to reduce the size of the army by thirty-five divisions to release additional manpower for the economy and scaled it down to a reduction of fifteen divisions.

Operation Sealion Figure 3: German Order of Battle mid September 1940: Luftwaffe and Navy
Operation Sealion Figure 3: German Order of Battle mid September 1940: Luftwaffe and Navy

Fuhrer Directive No. 16 issued on 16 July 1940 stated that the Wehrmacht would 'begin preparations for, and if necessary carry out, an invasion of England. The aim of this operation is to eliminate Great Britain as a base of operations from which the war against Germany can be fought and, if necessary, the island will be completely occupied.' An invasion would be carried out on a broad front and preparations completed by mid-August. The Luftwaffe would eliminate the RAF as an effective fighting force and interdict the Royal Navy should it try to intervene and the Kriegsmarine would furnish an invasion fleet and protect it. Current army plans would form the basis of the operation, although the line would be shortened slightly to between Ramsgate and the Isle of Wight. Hitler also confirmed that the operation would be codenamed Seelöwe (Sealion). In some ways, it seemed that the Luftwaffe was expected to almost defeat Britain by itself. Goring and his commanders however, mostly ignored the directive and continued with their own plans - they thought an invasion was going to be unnecessary anyway, while Raeder and the Kriegsmarine thought that OKW was insane. From this point, the Heer continued to be the main supporter of the plan, with the Luftwaffe lukewarm to the idea and the Kriegsmarine trying to torpedo the Heer's plan.

Operation Sealion Figure 4: German 16th Army Map No.8
Operation Sealion Figure 4: German 16th Army Map No.8

Following Fuhrer Directive No. 16, in which many historians highlight the words 'and if necessary carry out, an invasion' as an indication of Hitler's lack of commitment, the second half of July was filled with various staff meetings and proposals where the Luftwaffe confirmed it would be able to start a major air campaign against the RAF in early August but the Kriegsmarine would not be able to complete its preparations until mid-September. On 28 July 1940, they proposed that if the invasion were to go ahead that a beachhead be established near Dover, the closest point to the continent, where a narrow corridor could be protected by minefields to each side as well as groups of U-Boats and E-Boats beyond these. The Kriegsmarine estimated it would take ten days to put the first wave ashore and needless to say, the Heer was horrified. It had wanted landings all along the south coast from Folkestone to

Operation Sealion Figure 5: German plans for the Occupation of Britain
Operation Sealion Figure 5: German plans for the Occupation of Britain

Brighton with a separate landing from Cherbourg. It wanted wheeled and tracked vehicles and so all the car ferries were to be used along with all the cross-channel tourist facilities. The first wave was to be landed over three to four days and consist of 260,000 men, 30,000 vehicles and 60,000 horses. This was followed by a memo dated 31 July 1940, which advised that given the Kriegsmarine's preparations were complete by 15 September 1940, the dates most suitable for invasion would be from 22 - 26 September, when the weather was often bad. It could not however, guarantee to able to protect the invasion from the Royal Navy and would not be able to guarantee resupply if there was indeed bad weather. It was suggested that the invasion was put off until May 1941 when additional surface assets would be available and additional work be able to be carried out on converting or building vessels to allow for amphibious operations.

Operation Sealion Figure 6: British plans to resist the invasion
Operation Sealion Figure 6:
British plans to resist the invasion

Fuhrer Directive No. 17 was issued on 1 August 1940 (followed by one from OKW) and ordered the intensification of the air campaign against the RAF, targeting their air units, ground installations, observation facilities and aircraft factories. It also stated that all preparations for invasion would be completed by 15 September 1940, the original deadline being kept as Hitler was concerned over the strength of the British Army if the invasion was postponed until the following spring. Despite misgivings, the Kriegsmarine continued to scour the waterways

Operation Sealion Figure 7: Final German Invasion Plan
Operation Sealion Figure 7: Final German Invasion Plan

of occupied Europe for suitable craft, both powered and unpowered and proceeded to convert many of them by adding drop-down ramps, while the Heer conducted energetic landing exercises, with propaganda film crews in attendance. Mid-September saw the Kriegsmarine complete its assembly of the vessels to be used in the initial lift, as well as the finalisation of the German forces to be used (see Figures 2 and 3), the assault routes to be taken (see Figures 4 and 7), as well as the plans for occupation (see Figures 5 and 6).

Operation Sealion Figure 8: Location of German Second and Third Wave units
Operation Sealion Figure 8:
Location of German
Second and Third Wave units

Needless to say, the Luftwaffe’s defeat in the Battle of Britain forced Hitler to postpone the invasion on 17 September 1940 and then on 12 October 1940 postpone it until the following year. In any case, by then, Hitler’s attention had moved eastwards and was focused on his main ideological opponent, the USSR, with planning and preparations being undertaken for Operation Barbarossa.

List of Sources


Boylan, Kevin. 'Historical Commentary' in the playbook for Britain Stands Alone, GMT Games, Hanford C.A., 1994.
Campbell, John P. ‘A British Plan to Invade England, 1941’ in The Journal of Military History, Vol. 58, No. 4, October 1994, pp. 663 – 684.
Crawford, John. 'The Navy Lark!' in The Journal, Spring 2007, Issue 57, pp. 26 – 32.
Davis, Frank. ‘Sea Lion: The German Plan to Invade Britain, 1940’ in Bartlett, M. Assault from the Sea, Naval Institute Press, Annapolis, 1983, pp. 228 – 235.
Davis, Frank. 'Seelöwe: The German Plan to Invade Britain, 1940' in Strategy and Tactics, No. 40, September / October 1973, pp. 20 – 33.
Elstein, David. ‘Operation Sealion: The Plan to Invade Britain’ in History of the Second World War, Volume 1, Number 11, pp. 300 – 308.
Leonidov, A. 'The Fate That Was In Store For Britain' in International affairs, Number 6, Volume 6 (1960), pp. 65 – 71.
Lofthouse, Michael. 'British Order of Battle, 30th September 1940' in The Journal, Winter 2006, Issue 56, pp. 8 – 12.
Macksey. Kenneth. ‘Would Britain have Resisted?’ in World War II Investigator, October 1988, pp. 7 – 11.
Plehwe, Friedrich-Karl von. ‘Operation Sealion 1940’ in Royal United Services Institute Journal, March 1973, pp. 47 – 53.
Ray, Christopher. '1940 – 41 Britain's Finest Hour or Hitler's Greatest Hoax?' in History Review, March 1997, Issue 27, pp. 33 – 37.
Sandell, Roger and Lambshead, John. 'Invasions and Invaders' in The Wargamer, Number 40, April 1985, pp. 6 – 10.
Schenk, Dr Peter. ‘Sealion – The Invasion That Never Was’ in After the Battle, No. 69, pp. 1 – 19.
Smith, S C. 'Operation Sealion – 1940, Part 1 – Assault Vessels' in The Journal, Spring 1998, Issue 29, pp. 84 – 88.
Smith, S C. 'Operation Sealion – 1940, Part 2 – Wargames Scenarios' in The Journal, Summer 1998, Issue 30, pp. 56 – 62.
Tucker, Anthony. 'Operation Sealion: Myth or Reality?' in Wargames Illustrated, February 1989 to April 1989.
Werbaneth, James P. 'Operation Sea Lion: England's Final Hour?' in Command magazine, Issue 45, October 1997, pp. 42 – 59.
Wills, Henry. ‘British Invasion Defences’ in Ramsey, Winston G. (Ed) After the Battle, Number 14, 1976, pp. 38 – 46.
Wise, Terry. 'Operation Sealion' - a series of articles in Airfix Magazine from June 1975 to May 1976. These were: 'Operation Sealion – The Non-Invasion', June 1975, Vol 16, No. 10; 'Operation Sealion – British Forces', July 1975, Vol 16, No. 11; 'Operation Sealion - Dad's Army', August 1975, Vol 16, No. 12; 'Operation Sealion - German Plans', September 1975, Vol 17, No. 1; 'Operation Sealion - German Forces', October 1975, Vol 17, No. 2; 'Operation Sealion - Wargaming', November 1975, Vol 17, No. 3; 'Operation Sealion - Wargaming (cont)', December 1975, Vol 17, No. 4; 'Operation Sealion as a Wargame - Nautical Models', January 1976, Vol  17, No. 5; 'Operation Sealion as a Wargame', April 1976, Vol 17, No. 8; 'Operation Sealion as a Wargame', May 1976, Vol 17, No. 9.


Erich Raeder - Admiral of the Third Reich, Keith W. Bird. Looks at the full career of the first commander-in-chief of Hitler’s navy, a man who was often overshadowed by his successor Donitz and his U-boat war, but who played a major part in shaping the Kriegsmarine, both physically and politically. Undermines his claims to have been a non-political leader, and shows how close he was to the Nazi leadership, before eventually their different views of Germany’s war aims, and Hitler’s rather unrealistic expectations of the Navy forced his resignation(Read Full Review)
cover cover cover


Alexander, Colin. Ironsides Line: The Definitive Guide to the General Headquarters Line Planned for Great Britain in Response to the Threat of German Invasion 1940-1942, Historic Military Press, Storrington, 1999.
Angell, Stewart. The Secret Sussex Resistance, Middleton Press, Midhurst, 1996.
Ansel, Walter. Hitler Confronts England, Duke University Press, Durham, N.C., 1960.
Bird, Christopher. Silent Sentinels: The Story of Norfolk's Fixed Defences during the Twentieth Century, Larks Press, Dereham, 2001 (reprint).
Bodleian Library. German Invasion Plans for the British Isles 1940, University of Oxford, Oxford, 2007.
Brayley, Martin. The British Army 1939 – 45 (1) North-West Europe, Osprey Publishing Ltd, Oxford, 2001, Men-at-Arms Series No. 354.
Burridge, David. 20th Century Defences in Britain: Kent, Brassey's, 1997.
Butler, Chris. East Sussex Under Attack, The History Press, Stroud, 2007.
Butler, Chris. West Sussex Under Attack, The History Press, Stroud, 2008.
Carvell, Steve. Twentieth Century Defences in Warwickshire, Tempus Publishing, Stroud, 2007.
Clarke, Comer. England Under Hitler, New English Library, London, 1972.
Cocks, A E. Churchill's Secret Army 1939 – 45 and Other Recollections, The Book Guild Ltd, Lewes, 1992.
Collier, Basil. Defence of the United Kingdom, History of the Second World War: United Kingdom Military Series, Naval & Military Press Ltd, Uckfield, 2006.
Cruikshank, D. Invasion: Defending Britain from Attack, Boxtree, London, 2001.
Deighton, Len. Blitzkrieg, Granada, London, 1981.
Evans, Martin M & McGeoch, Angus. Invasion: Operation Sealion 1940, Longman, London, 2004.
Fleming, Peter. Invasion 1940, Rupert Hart-Davis, London, 1957.
Foot, William. Beaches, Fields, Streets and Hills, Council for British Archaeology, York, 2006.
Foot, William. Defended England 1940: The South-West, Midlands and North, Tempus Publishing, Stroud, 2008.
Foot, William. The Battlefields That Nearly Were, Tempus Publishing, Stroud, 2006.
Forty, George. British Army Handbook 1939 – 1945, Sutton Publishing, Stroud, 2002.
Foster, Joe. The Guns of the North-East: Coastal Defences from the Tyne to the Humber, Pen & Sword, Barnsley, 2004.
Gilbert, Adrian. Britain Invaded: Hitler’s Plans for Britain – A Documentary Reconstruction, Century, London, 1990.
Gillies, Midge. Waiting for Hitler – Voices from Britain on the Brink of Invasion, Hodder & Stoughton, London, 2006.
Glover, Michael. Invasion Scare – 1940, Pen & Sword Books, Barnsley, 1990.
Green, Major M. Warwalks: Stop Line Green, Reardon Publishing, Leckhampton, 1999.
Grinell-Milne, Duncan. The Silent Victory – September 1940, London, 1954.
Hayward, James. The Bodies on the Beach, CD41 Publishing, Dereham, 2001.
Hewitt, Geoff. Hitler's Armada – The Royal Navy and the Defence of Great Britain, April – October 1940, Pen & Sword Maritime Books, Barnsley, 2008.
Kieser, Egbert. Hitler on the Doorstep – Operation Sealion: The German Plan to Invade Britain 1940, Arms and Armour Press, London, 1997.
Klee, Karl. Unternehmen Seelowe, 2 Volumes, Musterschmit-Verlag, Gottingen, 1958 & 1959.
Lampe, David. The Last Ditch, G P Putnam & Sons, New York, 1968. This has now been republished with a forward from Gary Sheffield by Greenhill Books, London in February 2007.
Lavery, Brian. We Shall Fight Them on the Beaches: Defying Napoleon and Hitler 1805 and 1940, US Naval Institute Press, Annapolis, MD, 2009.
Longmate, Norman. If Britain Had Fallen, BBC / Hutchinson, London, 1972.
Longmate, Norman. Island Fortress: The Defence of Great Britain 1603 – 1945,
Longmate, Norman. The Real Dad's Army, Arrow, 1974.
Lowry, Bernard. 20th Century Defences in Britain – An Introductory Guide, Council for British Archaeology, 1995.
Lowry, Bernard. British Home Defences 1940 – 45, Osprey Publishing, Oxford, 2004, Fortress Series No. 20.
Lowry, Bernard. Discovering Fortifications from the Tudors to the Cold War, Shire Publications Ltd, 2006.
Lucas, James. German Army Handbook 1939 – 1945, Sutton Publishing, Stroud, 2002.
McCutcheon, Campbell. (Ed) Home Guard Manual 1941, Tempus Publishing, Stroud, 2007.
McLynn, F. Invasion: From the Armada to Hitler 1588 – 1945, Routledge & Kegan Paul, London, 1987.
MLRS Books. The Role of the Luftwaffe in Operation Sealion, MLRS Books, Buxton, 2006.
Osborne, Mike. 20th Century Defences in Britain: Cambridgeshire, Concrete Publications, Market Deeping, 2001.
Osborne, Mike. 20th Century Defences in Britain: The London Area, Concrete Publications, Market Deeping, 2006.
Osborne, Mike. Defending Britain: Twentieth Century Military Structures in the Landscape, Tempus Publishing, Stroud, 2004.
Osborne, Mike. Pillboxes of Britain and Ireland, Tempus Publishing, Stroud, 2008.
Necker, Wilhelm. Hitler's War Machine and the Invasion of Britain, Lindsay Drummond, London, 1941.
Robinson, Derek. Invasion, 1940: The Truth about the Battle of Britain and What Stopped Hitler, Constable, London, 2005.
Saunders, A J. English Heritage Book of the Channel Defences, B T Batsford, London, 1997.
Saunders, Ian. Pillboxes: Images of an Unfought Battle, Lulu Press Inc., Morrisville, NC, 2005.
Schellenburg, SS General Walter (with an introduction by Prof. John Erikson). Invasion 1940, St Ermin’s Press, London, 2001.
Schenk, Peter.  Invasion of England 1940: The Planning of Operation Sealion, Conway Maritime Press, London, 1990.
Sheers, Owen. 'Guerrillas in Waiting' in The Guardian, 20 October 2007, also located at http://www.guardian.co.uk/lifeandstyle/2007/oct/20/weekend.owensheers as of 02 October 2009.
Taylor, Telford. The Breaking Wave: The German Defeat in the Summer of 1940, Weidenfeld & Nicolson, London, 1967.
Taylor, Telford. The March of Conquest: The German Victories in Western Europe, Edward Hulton, London, 1959.
Thomas, Nigel. The German Army 1939 – 45 (1) Blitzkrieg, Osprey Publishing Ltd, Oxford, 1997, Men-at-Arms Series No. 311.
Ward, Arthur. Resisting the Nazi Invader, Constable & Co, London, 1997.
Warner, Philip. Invasion Road, Cassell Ltd, London, 1980.
Warwicker, John. Churchill’s Underground Army, Frontline Books, Barnsley, 2008.
Warwicker, John. With Britain in Mortal Danger, Cerberus Publishing, Bristol, 2002.
Wilks, Mick. The Defence of Worcestershire and the Southern Approaches to Birmingham in World War II, Logaston Press, Little Logaston, 2007.
Williamson, Alan. East Ridings Secret Resistance, Middleton Press, Midhurst, 2004.
Wills, Henry. Pillboxes: A Study of UK Defences 1940, Leo Cooper / Secker and Warburg, 1985.
Wilmot, Chester. The Struggle for Europe, Collins, 1952.
Wheatley, Ronald. Operation Sealion, Oxford University Press, London, 1958.

Chapters in Edited Books

Badsey, Stephen. 'Disaster at Dunkirk: The Defeat of Britain, 1940' in Tsouras, Peter G. (Ed) Third Reich Victorious, Greenhill Books, London, 2002.
Macksey, Kenneth. 'Operation Sea Lion: Germany Invades Britain, 1940' in Macksey, Kenneth. The Hitler Options: Alternate Decisions of World War II, Greenhill Books, London, 1995.
Roberts, Andrew and Ferguson, Niall. ‘Hitler’s England: What If Germany had Invaded Britain in May 1940?’ in Ferguson, Niall (Ed). Virtual History: Alternatives and Counterfactuals, Picador, London, 1997.
Wallach, Jehuda L. 'The Sea Lion That Did Not Roar: Operation Sea Lion and its Limitations' in Hattendorf John B and Murfett, Malcolm H. The Limitations of Military Power, MacMillan, London 1990, pp. 173 – 202.

Internet Resources

Axis History Factbook. Order of Battle – Unternehmen Seelowe (Sealion) Webpage located at http://www.axishistory.com/index.php?id=1145 as of 08 January 2007.
Barrett, Steve. Steve Barrett Books Website detailing historical information about Operation Sealion as well as the opportunity to buy a copy of the author's own alternate history novel regarding the operation, entitled 'Sealion'. Located at http://www.stevebarrettbooks.com/index.htm, active as of 16 January 2005.
British Resistance Museum. The Museum of the British Resistance Organisation, located at http://www.parhamairfieldmuseum.co.uk/brohome.html as of 18 August 2009. Museum is located at Parham Airfield, Framlingham, Suffolk.
Carter, Tim. Pillboxes web page at http://www.geocities.com/pentagon/camp/3224/ as of 04 June 2998.
Cruikshank, Dan. The German Threat to Britain in World War Two Webpage, at http://www.bbc.co.uk/history/worldwars/wwtwo/invasion_ww2_01.shtml, part of the BBC History Website, 30 January 2007.
Defence of Britain Project homepage, currently located at http://www.britarch.ac.uk/projects/dob/ as of 15 May 2008.
Farrant, David. WW2 & Cold War History in Britain website, currently located at http://www.century20war.co.uk/ as of 04 June 2008.
Flin, David and Brooks, Alison. Why Sealion is not an option for Hitler to win the war webpage, currently located at http://www.flin.demon.co.uk/althist/seal1.htm, as of 08 January 2007.
History Learning Site. Operation Sealion Webpage located at http://www.historylearningsite.co.uk/operation_sealion.htm, active as of 16 January 2005.
Montgomerie, Ian. Why Operation Sealion Wouldn't Work webpage, currently located at http://gateway.alternatehistory.com/essays/Sealion.html, as of 08 January 2007.
Parker, Larry. 'Sea Lion vs. Overlord' webpage, Military History Online website at http://www.militaryhistoryonline.com/wwii/articles/sealionvsoverlord.aspx as of 08 January 2007.
Pillbox Study Group website, currently located at http://www.pillbox-study-group.org.uk/ as of 04 June 2008.
Saunders, Ian. World War 2 Pillboxes and Invasion Defences in the UK Website, currently located at http://www.pillboxesuk.co.uk, active as of 4 September 2005.
Simon Wiesenthal Centre. Operation Sealion Webpage currently located at
http://motlc.wiesenthal.com/text/x20/xm2033.html and active as of 17 January 2005.
Spartacus Schoolnet. Operation Sealion Webpage, located at http://spartacus-educational.com/2WWsealoin.htm, active as of 16 January 2005.
Stone & Stone Website has a bibliography page listing a number of books, located at
http://books.stonebooks.com/cgi-bin/foxweb.exe/base/subjects?1000167, active as of 17 January 2005.
Sykes, Tom. Coleshill House - Home of Churchill's Underground Army Website, located at http://www.coleshillhouse.com/ as of 18 August 2009 (Coleshill Auxiliary Research Team).
Waller, David. Auxiliary Unit News Website, located at http://www.auxunit.org.uk/ as of 18 August 2009.
Wikipedia. British Anti-Invasion Preparations of World War II Webpage, currently at http://en.wikipedia.org/wiki/British_anti-invasion_preparations_of_World_War_II as of 25 March 2007.
Wikipedia. Operation Sealion Webpage, currently located (as of 22 January 2007) at http://en.wikipedia.org/wiki/Operation_Sealion.


Calendar 1937 – Booklet detailing sabotage and guerrilla warfare techniques.
Calendar 1938 – Booklet detailing sabotage and guerrilla warfare techniques.
Dawes, Maj E J M. Defeating Organised Resistance Networks: Are There Lessons In History?, Defence Research Paper, Advanced Command and Staff Course No. 7, Joint Services Command and Staff College, September 2003 – July 2004.
Grylls, Ch. Off. C F. What Factors Led to Hitler's Decision not to Invade Britain in 1940 Despite his Military Success?, Defence Research Paper, Advanced Command and Staff Course No. 10, Joint Command and Staff College, September 2007 – July 2007.
Gubbins, Col Colin M. Partisan Leader's Handbook: Principles of Guerilla Warfare and Sabotage. Booklet detailing sabotage and guerrilla warfare techniques.
Gubbins, Col Colin M. The Art of Guerilla Warfare. Booklet detailing sabotage and guerrilla warfare techniques.
Maskell, Maj A J. Let Us Go Forward Together: How Did the Political and Military Strategic Environment in 1940 Influence Planning for the Defence of the United Kingdom?, Defence Research Paper, Advanced Command and Staff Course No. 9, Joint Services Command and Staff College, September 2005 – July 2006.
Olson, Greg D. McCanne, Randy & Teicher, Dario E. Operation Sea Lion: A
Joint Critical Analysis
. Joint Forces Staff College, National Defence
University, Norfolk, VA, 2002 (available at http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA421637&Location=U2&doc=GetTRDoc.pdf).
Ruddy, Austin J. British Anti-Invasion Defences 1940 – 1945, Historic Military Press, Pulborough, 2003.
Taylor, Andy (Ed) Auxiliary Units: History and Achievement 1940 – 1944, Gripping Press, Needham Market, 1998. From an original document by Major N V Oxenden MC, written in October 1944 and discovered by the British Resistance Organisation Museum, Parham Airfield, Framlingham, Suffolk.
Highworth & Co. The Countryman's Diary 1939 (Highworth's Fertilisers). Booklet detailing sabotage and guerrilla warfare techniques.
Warren. Derrick. Now You See It – Then You Didn’t! Inter-Channel Stop Line, Somerset Industrial Archaeological Society, SIAS Survey No. 14, 2000, ISBN: 0953353931.


Cox, Richard. Sealion, Futura Publications, London, 1977.
Deignton, Len. SS-GB, Triad Grafton, London, 1986 (Reprint).
Macksey, Kenneth. Invasion: The German Invasion of England, July 1940, Arms and Armour Press, London, 1980.
Stevens, Gordon. And All The King's Men, Pan Books, London, 1991.
Thayer, James S. S-Day: A Memoir of the Invasion of England, St Martin's Press, New York, 1990.

Official Publications

General Staff. Notes on German Preparations for Invasion of the United Kingdom, 2nd Edition, M.I.14, WOP 9372, January 1942.
German High Command (OKW). OKW Directives for the Invasion of UK. Operation Seelöwe (Sealion) Summer and Autumn1940, 2 July 1940 – 22 October 1940.
Highworth & Co. The Countryman’s Diary 1939: Highworth’s Fertilizers (Cover for a General Staff training booklet to teach members of the Auxiliary Units about explosive devices), 42 pp.
Parry, W E. (Director of Naval Intelligence) German Plans for the Invasion of England 1940 (Operation "SEALION"), NID24/GHS/1, London, February 1947.

Films / TV Documentaries / Docu-dramas

'The Post Mistress who was a Spy?', part of the History Mysteries series, 24 January 2006 at 3pm, BBC2 / Open University. Series Director: Samantha Bakhurst; Series Producer: Sally Angel.
Hitler and the Invasion of Britain, BBC2, aired on 07/04/1998, 50mins, part of the Timewatch series.
Hitler's Britain, Channel 5, Part One: 03/12/02, 60mins; Part Two: 10/12/02, 60mins.
Invasion, BBC2, Presenter: Dan Cruikshank. Three episodes aired between 28/10/2001 and 11/11/2001.
It Happened Here (1964), Directors: Kevin Brownlow / Andrew Mollo, 97mins, English/German, B&W, ASIN: B000CBOZWG, Studio: Film First.
The Real Dad's Army (2009), Channel 4, Part One: 10/01/09, 60mins; Part Two: 17/01/09, 60mins; Part Three: 24/01/09, 60mins. Note: There was another series entitled The Real Dad's Army, the fourth episode of which was hosted by Ian Lavender and was about the Auxiliary Units.
When Hitler Invaded Britain, ITV1, 04 July 2004, 22.15 – 23.45, 90 mins.

Wargame Resources

For those wanting to fight Operation Sealion, there are number of possibilities. For board wargamers, the US wargame manufacturer, SPI, produced a wargame entitled Seelöwe, designed by John Young and published in 1974, which only covered the ground campaign, assuming the Luftwaffe had decisively defeated the RAF and were in a position to block any Royal Navy intervention. The game also had a modified edition produced in the UK by SPI (UK) Ltd that had a colour map with greater detail. XTR produced a game called Operation Sealion by L. Dean Webb that was included in the magazine Command, issue number 45, published in October 1997. 3W also pitched in with a wargame entitled Fight on the Beaches by Roger Sandell and John Lambshead that accompanied The Wargamer magazine, Issue 40, published in April 1985. GMT Games of Hanford, CA produced a game in 1994 entitled Britain Stands Alone, designed by Jim Werbaneth. This covers the entire land-air-sea campaign for Operation Sealion and so is somewhat more complicated and time-consuming than Seelöwe, but the players can decide on their own strategy for the operation with the full ground, naval and air forces at their command. GDW produced a game entitled Their Finest Hour in 1982 that was designed by Jim Astell and part of the enormous Europa series of games (being volume five) that simulated World War II at the divisional level. Part of the game simulated the forces that would have been involved in Operation Sealion had the Luftwaffe won the Battle of Britain, which is in fact the main focus. There was also a wargame entitled Sea Lion from Wargaming Enterprises, designed by Mark Jumper produced in 1970 and I have seen a custom designed and built expansion for the Axis & Allies series of games entitled 'Operation: Sealion' from a company called Rune Blade Studios on eBay. There is also likely to be a future edition of the Strategy & Tactics magazine with a game devoted to the subject (see https://strategyandtacticspress.com/ for details of up-and-coming issues) and I’ve seen a Sealion related scenario for the game Memoir ‘44. For additional wargaming material, there is also Issue 13 of Ragnarok (the journal of fantasy and science fiction wargaming) and Issues 29, 30 and 56 of The Journal of the Society of Twentieth Century Wargamers. Any decent miniature wargame rules (such as Rapid Fire) should have the rules and order of battle coverage for someone to put together a Sealion scenario with a little work – in saying that, there is a specific supplement entitled 'Operation Sea Lion' produced by The Two Fat Lardies (http://www.toofatlardies.co.uk) for their 20mm wargames rules system I Ain't Been Shot Mum.

As far as PC wargaming is concerned, the official expansion pack for Talonsoft's West Front focused on Operation Sealion, and games such as Steel Panthers: World at War (Matrix Games), Steel Panthers for Windows – World War 2 (The Camo Workshop), Combat Mission (CDV) and Operational Art of War (Talonsoft) often have mission editors where you can build your own scenarios. There is even an extra map for Battlefield 1942 entitled 'Operation Sealion', which is just over 15Mb in size, from Bumsoft, and can be downloaded from the Filefront website at http://battlefield1942.filefront.com/file/Operation_Sea_Lion;35707.

For other ‘what-if’ operations by German forces during World War II, Avalon Hill’s 1977 game, Air Assault on Crete, designed by Randell C Reed and Vance von Borries has two such elements. The first is that a second game was included in the official Avalon Hill release that covers Operation Hercules, the proposed joint German – Italian invasion of Malta in 1942. There are also specific scenarios on Operation Hercules in Talonsoft's Operational Art of War and Conquest of the Aegean (third in the Airborne Assault series) from Panther Games, with an option to create your own scenarios in Combat Mission 3: Afrika Korps from CDV. Secondly, a scenario variation was included in Volume 18, No. 3 of The General, Avalon Hill’s wargaming magazine with its own board and counters that covered a possible parachute assault on Cyprus. There was also a boardgame entitled Operation Felix that was included with Strategy & Tactics magazine, Number 153 (1992) and looked at the planned German assault on Gibraltar in either 1940 or 1941.


(1) See for example http://www.telegraph.co.uk/news/newstopics/world-war-2/battle-of-britain/8012065/Battle-of-Britain-service-Prince-Charles-and-Prince-William-lead-tributes-to-The-Few.html.

WWII Home Page | WWII Subject Index | WWII Books | WWII Links | Day by Day

How to cite this article: Antill, P, (20 October 2010), Operation Sealion: The Planned German Invasion of Britain A Primer and List of Sources, http://www.historyofwar.org/articles/operation_sealion_primer.html

Help - F.A.Q. - Contact Us - Search - Recent - About Us - Privacy