The Opening Campaigns
September 1939 to June 1941 · Poland, Scandinavia, the West and the Balkans · Six operations
Twenty-one months in which Germany took almost everything it would ever hold. Poland in five weeks, Denmark in six hours, Norway in two months, the Netherlands in five days, France in six weeks. Then it reached the Channel and stopped, because the thing that had worked on land did not work on water.
Bundesarchiv Bild 101I-299-1808-10A · CC BY-SA 3.0 DE · Source
- SPAN
- 21 months1 September 1939 to 1 June 1941
- CAMPAIGN PAGES
- EightPoland, Winter War, Norway, France, Battle of Britain, Yugoslavia, Greece and Crete
- WAR WIDENS
- 3 September 1939Britain and France declare war on Germany after the invasion of Poland
- GERMAN ADVANCE CHECKED
- Battle of BritainThe Luftwaffe fails to achieve the air superiority required for Operation Sea Lion
- LISTING ENDPOINT
- 1 June 1941Organised Allied resistance on Crete ends three weeks before Operation Barbarossa
Europe at War, 1939–1941
Why these eight campaigns sit together in one listing.The opening period of the European war moved between very different theatres and military problems. Poland was attacked from west, north, south and then east. Finland fought the Soviet Union in terrain and winter conditions unlike the campaigns farther south. Norway turned control of ports, sea lanes and airfields into the centre of the war. France was decided by a rapid operational penetration whose consequences reached the Channel before the Allied command could reconstruct a continuous front.
Britain then presented a different obstacle. A cross-Channel invasion required air superiority and maritime conditions that German success on land had not supplied. In spring 1941 the war shifted again to Yugoslavia, Greece and Crete, where political collapse, mountain routes, expeditionary forces, naval evacuation and airborne assault produced another set of problems.
The listing ends with Crete because the next German campaign changed the scale and direction of the continental war. Operation Barbarossa opened on 22 June 1941; from that point the Eastern Front becomes its own theatre, while the Mediterranean, Atlantic and occupation wars develop on separate tracks.
Eight Campaigns
Each card opens a dedicated campaign page with its own chronology, maps, sources and operational analysis.The sequence is chronological rather than triumphal. Germany wins most of the continental campaigns listed here, but the Winter War belongs because Soviet performance influenced how European staffs assessed the Red Army, and the Battle of Britain belongs because it marks the first major strategic objective in this sequence that Germany failed to secure.
Yugoslavia, Greece and Crete remain separate pages even though they overlap in one Balkan campaign. Their command structures, terrain, defenders and military methods differ enough that merging them would hide more than it would simplify.
The Invasion of Poland
Germany and Slovakia invaded Poland on 1 September. Polish armies fought forward to protect major population and industrial regions, then withdrew as German armoured formations repeatedly threatened their flanks and rear. The Bzura counteroffensive forced a substantial German reaction but could not reopen the strategic situation around Warsaw.
Britain and France declared war on 3 September, turning the campaign into a general European war, but no western offensive developed on a scale that could pull major German forces out of Poland. On 17 September the Soviet Union invaded from the east under the political settlement created by the German-Soviet pact.
The Winter War
The Soviet Union invaded Finland on 30 November 1939 expecting a rapid result. On the Karelian Isthmus Finnish forces used prepared positions to slow the main Soviet concentration, while farther north small units exploited forest roads, snow and local mobility against columns that were difficult to support or deploy.
The early Soviet failures were severe, but the Red Army adapted. Command arrangements were revised, artillery and engineering strength were concentrated, and renewed attacks in February broke through the Mannerheim Line. Finland faced the prospect of deeper penetration without the outside military intervention its government had hoped might arrive.
Weserübung, Denmark and Norway
Germany attacked Denmark and Norway on 9 April in a combined operation using warships, transports, aircraft and airborne troops to seize a chain of ports and airfields before Allied forces could establish themselves. Denmark capitulated quickly; Norway became a two-month campaign spread along an exceptionally long coast.
At Oslo, Oscarsborg Fortress sank the heavy cruiser Blücher and delayed the occupation of the capital long enough for the Norwegian government and royal family to escape. Around Narvik, German and Allied naval forces suffered heavy losses while British, French, Polish and Norwegian troops fought for the port and the iron-ore route.
The Fall of France
Germany attacked the Netherlands, Belgium, Luxembourg and France on 10 May. The Allied armies moved north toward the expected battle in Belgium while the principal German armoured concentration crossed the Ardennes and forced the Meuse at Sedan, Dinant and Monthermé.
The German drive to the Channel cut the British Expeditionary Force and major French and Belgian formations away from the armies farther south. More than 300,000 Allied troops were evacuated through Dunkirk, preserving manpower while abandoning most heavy equipment. The evacuation did not restore the French strategic position.
The Battle of Britain
After France fell, the Luftwaffe fought for air superiority over the Channel and southern England while German staffs prepared Operation Sea Lion. Fighter Command's defence linked radar warning, Observer Corps reporting, filter and group headquarters, sector control and squadrons into one system.
The fighting placed No. 11 Group and several sector stations under real strain. The shift of the main German effort toward London on 7 September relieved some pressure on the airfield system, but it did not rescue a force otherwise certain to collapse. German intelligence had underestimated Fighter Command's remaining strength and the Luftwaffe continued to incur losses it could not convert into air supremacy.
The Invasion of Yugoslavia
Germany attacked Yugoslavia on 6 April after the 27 March coup had overturned the government that signed the Tripartite Pact. German forces struck from several directions while Italian and Hungarian forces joined the campaign and the Luftwaffe attacked Belgrade and airfields.
The Yugoslav Army was still mobilising across an exceptionally long frontier and suffered from weak communications, political fragmentation and a plan that could not concentrate effectively against converging attacks. German mobile forces entered Belgrade on 12 April and the military capitulation was signed on 17 April.
The Invasion of Greece
Greece had been fighting Italy since October 1940 and had pushed much of the Italian front back into Albania. Germany opened Operation Marita on 6 April from Bulgaria while the simultaneous destruction of Yugoslavia created a route into northern Greece behind parts of the prepared defensive system.
The Metaxas Line resisted frontal attacks, but German armoured forces moving through Yugoslavia reached the Thessaloniki area and made continued defence of the eastern forts operationally impossible. Farther west, the British-Commonwealth expeditionary force and Greek formations withdrew south as German columns threatened their routes.
The Battle of Crete
German airborne forces attacked Crete on 20 May around Maleme, Chania, Rethymno and Heraklion. The first day produced severe losses and no clean island-wide success. The critical change occurred around Maleme, where the Germans gained use of the airfield and could fly in mountain troops and supplies.
The Royal Navy intercepted attempts to reinforce the island by sea but operated under overwhelming German air attack, losing three cruisers and six destroyers during the campaign while other major ships were damaged. Allied ground forces withdrew toward evacuation points on the south coast as German strength increased.
Sources & Archives
The listing uses the same source hierarchy as the campaign pages, with national records and official histories preferred over inherited summaries.Poland is checked against Polish archival and institutional material alongside German records; the Winter War against Finnish archival sources and Soviet loss studies; Norway and France against British official histories, national archives and German operational records. The Battle of Britain uses RAF campaign histories and the documented invasion-planning record.
For Yugoslavia, Greece and Crete, the page uses German, Yugoslav, Greek and British records together. This matters because German wartime descriptions often emphasised speed and collapse, while the defending states' archives preserve mobilisation problems, local resistance, withdrawals and the political consequences that continued after the front moved on.
- The September Campaign 1939 — Polish records and campaign studiesInstytut Pamięci Narodowej
- Winter War operational records and photographsNational Archives of Finland / SA-kuva
- The Campaign in Norway, United Kingdom Military Series, T. K. Derry, 1952HMSO
- German and Allied plans for Norway, spring 1940National Archives of Norway
- The War in France and Flanders 1939–1940, United Kingdom Military Series, L. F. Ellis, 1953HMSO
- Campaign in France and the Low Countries, September 1939–June 1940Royal Air Force, Air Historical Branch
- Air Defence of Great Britain, Volume II: The Battle of BritainRoyal Air Force, Air Historical Branch
- Operation Sea Lion and the requirement for air superiorityRoyal Air Force Museum
- The destruction of Yugoslavia in the Second World WarBundesarchiv
- The Yugoslav Army in the April War of 1941, Slobodan DjukicMilitary Historical Review
- The Battle of the Forts, 6–9 April 1941Hellenic Army historical portal
- The Mediterranean and Middle East, Volume II: The Germans Come to the Help of Their Ally (1941), I. S. O. Playfair et al., 1956HMSO
- The German airborne invasion of Crete, May–June 1941Deutsches Historisches Museum
- Operation DynamoRoyal Air Force
- Europe at the end of August 1939, historical basemap, San JoseWikimedia Commons · Public domain · palette and labels adapted for this site
Operation chronologyDates, locations and sourced event summaries
| Date | Event | Location | Summary |
|---|---|---|---|
| 1 September to 6 October 1939 · 01 | The Invasion of Poland | Poland | Germany and Slovakia invaded Poland on 1 September. Polish armies fought forward to protect major population and industrial regions, then withdrew as German armoured formations repeatedly threatened their flanks and rear. The Bzura counteroffensive forced a substantial German reaction but could not reopen the strategic situation around Warsaw. Sources 1 |
| 30 November 1939 to 13 March 1940 · 02 | The Winter War | Finland and Karelia | The Soviet Union invaded Finland on 30 November 1939 expecting a rapid result. On the Karelian Isthmus Finnish forces used prepared positions to slow the main Soviet concentration, while farther north small units exploited forest roads, snow and local mobility against columns that were difficult to support or deploy. Sources 2 |
| 9 April to 10 June 1940 · 03 | Weserübung, Denmark and Norway | Denmark and Norway | Germany attacked Denmark and Norway on 9 April in a combined operation using warships, transports, aircraft and airborne troops to seize a chain of ports and airfields before Allied forces could establish themselves. Denmark capitulated quickly; Norway became a two-month campaign spread along an exceptionally long coast. Sources 3, 4 |
| 10 May to 22 June 1940 · 04 | The Fall of France | France and the Low Countries | Germany attacked the Netherlands, Belgium, Luxembourg and France on 10 May. The Allied armies moved north toward the expected battle in Belgium while the principal German armoured concentration crossed the Ardennes and forced the Meuse at Sedan, Dinant and Monthermé. Sources 5, 6, 14 |
| 10 July to 31 October 1940 · 05 | The Battle of Britain | Southern England and the Channel | After France fell, the Luftwaffe fought for air superiority over the Channel and southern England while German staffs prepared Operation Sea Lion. Fighter Command's defence linked radar warning, Observer Corps reporting, filter and group headquarters, sector control and squadrons into one system. Sources 7, 8 |
| 6 to 17 April 1941 · 06A | The Invasion of Yugoslavia | Yugoslavia | Germany attacked Yugoslavia on 6 April after the 27 March coup had overturned the government that signed the Tripartite Pact. German forces struck from several directions while Italian and Hungarian forces joined the campaign and the Luftwaffe attacked Belgrade and airfields. Sources 9, 10 |
| 6 to 30 April 1941 · 06B | The Invasion of Greece | Mainland Greece | Greece had been fighting Italy since October 1940 and had pushed much of the Italian front back into Albania. Germany opened Operation Marita on 6 April from Bulgaria while the simultaneous destruction of Yugoslavia created a route into northern Greece behind parts of the prepared defensive system. Sources 11, 12 |
| 20 May to 1 June 1941 · 06C | The Battle of Crete | Crete | German airborne forces attacked Crete on 20 May around Maleme, Chania, Rethymno and Heraklion. The first day produced severe losses and no clean island-wide success. The critical change occurred around Maleme, where the Germans gained use of the airfield and could fly in mountain troops and supplies. Sources 12, 13 |
Image rights and editorial standard. Bundesarchiv files retain the licence stated on their exact Wikimedia Commons file pages. Finnish SA-kuva material is credited under the reuse licence on its individual record; British official photography is used under the status stated on the relevant Commons or IWM record. Hero and campaign-card media point to exact file pages rather than category or generic archive pages. The map states are generalised orientation graphics for a theatre listing page, not survey-accurate operational fronts. Each campaign summary is a gateway to its dedicated page and therefore preserves context without attempting to replace the fuller chronology.