| December 1939 |
| December 1st, 1939 |
| Winter War: The Soviet Union intensifies its invasion of Finland, launching coordinated ground and air assaults along the Karelian Isthmus. Finnish defenders, despite being outnumbered, use fortified positions and guerrilla tactics to stall Soviet advances. The Soviet Army struggles with logistical issues and unfamiliar terrain. |
| Battle of the Atlantic: German U-boats continue targeting British merchant shipping. The Royal Navy deploys additional escort vessels, adjusting convoy routes to avoid U-boat-infested waters. |
| December 2nd, 1939 |
| Winter War: Heavy snowfall in Finland hampers both Soviet and Finnish movements. Soviet forces attempt to breach the Mannerheim Line but suffer heavy casualties as Finnish defenders effectively utilise terrain advantages and well-placed artillery. |
| Second Sino-Japanese War: Japanese forces advance deeper into Guangxi province, securing key supply lines. The Chinese resistance launches small-scale counterattacks but is unable to halt Japanese progress. |
| December 3rd, 1939 |
| Winter War: The Soviet Air Force increases bombing raids on Finnish cities and defensive positions. Helsinki, Viipuri, and other major settlements experience significant damage. |
| Finland seeks support on the Winter War: Finland pleads with Britain and France for assistance, but direct military aid remains limited due to logistical difficulties. |
| Preperations Fall Gelb: Hitler meets with military advisors to discuss final adjustments to the upcoming Western offensive. Weather conditions delay initial timetables. |
| December 4th, 1939 |
| Winter War: Finnish forces execute a successful ambush on Soviet supply lines near Suomussalmi, disrupting Red Army logistics. Soviet troops begin suffering from frostbite and food shortages as winter conditions worsen. |
| Great Britain prepares for War: The British War Cabinet debates extending the blockade on Germany, further restricting imports of strategic materials to slow German war production. |
| December 5th, 1939 |
| Winter War: Soviet reinforcements arrive on the Finnish front, but Soviet Army commanders struggle to coordinate large-scale operations. Finnish ski troops continue hit-and-run tactics against Soviet supply convoys. |
| Great Britain prepares for War: The Royal Navy reinforces the Scapa Flow base, preparing for possible German naval incursions. |
| December 6th, 1939 |
| Great Britain and France prepare for War: The first British Commonwealth troops begin arriving in France to support the British Expeditionary Force. France continues reinforcing defensive positions along the Maginot Line. |
| Second Sino-Japanese War: The Japanese Imperial Army strengthens its hold on occupied Chinese cities, implementing strict security measures to counteract guerrilla attacks. |
| December 7th, 1939 |
| Winter War: Soviet forces suffer another defeat at Suomussalmi as Finnish defenders execute a well-planned counteroffensive, encircling Soviet battalions. The Soviet Army loses significant numbers of men and equipment. |
| Great Britain prepares for War: British civil defence preparations continue as the government anticipates possible German air raids. |
| December 8th, 1939 |
| Winter War: The Soviet Union begins revising its strategic objectives in Finland, considering alternative approaches after continued battlefield setbacks. |
| Battle of the Atlantic: German naval planners consider expanding U-boat operations to the South Atlantic to further disrupt Allied supply routes. The Royal Navy increases patrols near Gibraltar and the North Sea. |
| December 9th, 1939 |
| Winter War: Finnish forces inflict heavy casualties on Soviet units attempting another breakthrough on the Karelian Isthmus. Reports emerge of low Soviet morale as harsh winter conditions take their toll. |
| Great Britain prepares for War: The Royal Air Force conducts additional reconnaissance missions over German industrial regions, monitoring war production facilities. |
| December 10th, 1939 |
| Winter War: The Soviet High Command orders a temporary halt to major offensives, reassessing invasion tactics after underestimating Finnish resistance. Soviet commanders begin planning a massive reorganisation of forces. |
| Battle of the Atlantic: German U-boats sink multiple Allied merchant ships. The Royal Navy scrambles to improve convoy escort strategies. |
| December 11th, 1939 |
| Great Britain and France try to support Finland: British and French military officials discuss sending supplies to Finland, but logistical hurdles prevent immediate action. |
| Great Britain negotiates with Scandinavia: Diplomatic efforts intensify as Great Britain seeks to maintain Scandinavian neutrality while undermining Soviet aggression. |
| Second Sino-Japanese War: The Japanese military secures further positions in China, but resistance fighters continue launching sporadic attacks on supply lines. |
| December 12th, 1939 |
| Winter War: The Soviet Union introduces heavier artillery and armoured support in Finland, planning another offensive despite repeated failures. Finnish intelligence intercepts Soviet communications, providing advance warnings to key defensive units. |
| Great Britain prepares for War: The British government expands aircraft production, ensuring continued development of the Royal Air Force’s fighter and bomber capabilities. |
| December 13th, 1939 |
| Battle of the Atlantic: The Battle of the River Plate takes place in the South Atlantic. British warships, led by H.M.S. Exeter, H.M.S. Ajax, and H.M.S. Achilles, engage the German pocket battleship Admiral Graf Spee. The German ship suffers damage and retreats toward Montevideo, Uruguay. |
| Winter War: Finnish ski troops continue disrupting Soviet supply routes, using small, highly mobile units to ambush convoys. |
| December 14th, 1939 |
| Winter War: The Soviet Red Army launches another assault on the Mannerheim Line, but Finnish defenders hold firm. Soviet casualties mount as coordinated Finnish artillery and infantry counterattacks repel enemy advances. |
| Great Britain and France negotiate with Scandinavia: The British and French governments continue debating intervention in Scandinavia, weighing the risks of direct involvement against the strategic benefits of aiding Finland. |
| December 15th, 1939 |
| Battle of the Atlantic: The Kriegsmarine begins exploring alternative strategies for raiding Allied shipping in the Atlantic, focusing on wolf pack tactics to maximise U-boat effectiveness. |
| Second Sino-Japanese War: Japanese forces consolidate newly occupied territories while Chinese resistance fighters continue waging guerrilla warfare in the countryside. |
| December 16th, 1939 |
| Winter War: Soviet bombers target Finnish railways and supply depots, attempting to disrupt reinforcements. The Finnish military maintains mobility, using the country’s vast forested regions for effective defensive tactics. |
| Battle of the Atlantic: The Royal Navy issues new orders for convoy routes, increasing security measures against U-boat threats. |
| December 17th, 1939 |
| Battle of the Atlantic: The German pocket battleship Admiral Graf Spee is scuttled in the River Plate estuary off Montevideo after being cornered by British warships. The ship’s captain, Hans Langsdorff, chooses to destroy the vessel rather than risk its capture. |
| Winter War: Finnish forces continue scoring small tactical victories against Soviet invaders, frustrating Red Army commanders. |
| December 18th, 1939 |
| Battle of the Heligoland Bight: The first major air battle of the war between the Royal Air Force and the German Luftwaffe. The RAF’s Bomber Command dispatches 22 Vickers Wellington bombers on a daylight mission to attack German naval vessels in the Heligoland Bight, near Wilhelmshaven. German fighter aircraft intercept the bombers, resulting in the loss of 10 Wellingtons. This engagement leads the Royal Air Force to reconsider the viability of daylight bombing raids over Germany. |
| Winter War: The Soviet military receives additional reinforcements along the Finnish front, preparing for a renewed push. |
| Hitler congratulates Stalin: Adolf Hitler sends a telegram to Joseph Stalin on his 60th birthday, wishing him “good health and a happy future for the peoples of the friendly Soviet Union.” This message underscored the temporary non-aggression pact between Nazi Germany and the Soviet Union at that time. |
| December 19th, 1939 |
| Winter War: Finnish intelligence reports indicate that Soviet commanders are adjusting tactics in response to previous defeats. Finnish troops remain well-prepared for further engagements. |
| Winter War: Soviet forces launched coordinated air and ground attacks against Finnish defensive positions near Summa. |
| Battle of the Atlantic: Captain Hans Langsdorff of the German Pocket Battleship Admiral Graf Spee commits suicide in Buenos Aires, Argentina. |
| December 20th, 1939 |
| Winter War: Soviet forces regroup for another major attack on Finnish positions. |
| Great Britain prepares for War: The British War Cabinet reviews long-term strategic plans, assessing how best to counter German expansion without committing to an immediate offensive. |
| Fundraising for Finland: A rally titled “Let’s Help Finland” was held at Madison Square Garden in New York City to support the Finnish Relief Fund. Former U.S. President Herbert Hoover delivered a speech at the event, which was also broadcast to the American public. |
| December 22nd, 1939 |
| Winter War: The Soviet Army reinforces its frontline units, bringing in fresh divisions from the Soviet interior. However, logistical issues and extreme cold continue to hinder offensive operations. Finnish forces launched a strategic counteroffensive in the Petsamo region. Finnish ski troops conduct successful night raids on Soviet encampments, disrupting supply lines and morale. |
| Great Britain and France support Scandinavia: The British government considers sending military aid to Finland but faces significant logistical challenges. France explores potential troop deployments to Scandinavia to counter Soviet aggression. |
| December 23rd, 1939 |
| Winter War: Soviet air raids target Finnish cities and military depots, but Finnish anti-aircraft defences manage to shoot down several Soviet bombers. Finnish civilians begin widespread evacuations from targeted urban centres. |
| Germany prepares for War: The Kriegsmarine orders an increase in naval patrols along the Norwegian coast to monitor British fleet movements and ensure Germany’s access to key supply routes. |
| Canadian Troops Arrive in Britain: Approximately 7,500 Canadian soldiers landed in Great Britain. |
| Formation of MI9: The British established Military Intelligence Section 9 (MI9), a specialised unit tasked with aiding resistance fighters, downed airmen, and prisoners of war in Nazi-occupied territories. |
| December 24th, 1939 |
| Winter War: The Finnish Army achieves a decisive victory at the Battle of Suomussalmi, encircling and annihilating a Soviet division. This battle solidifies Finland’s reputation for tactical ingenuity and exposes severe weaknesses in Soviet command and logistics. |
| British King’s Speech: King George VI delivers a Christmas broadcast, urging the British people to remain steadfast in the face of war. British Troops stationed in France observe the holiday with minimal festivities, as preparations for future engagements continue. |
| December 25th, 1939 |
| Winter War: Fighting slows temporarily on Christmas Day, though skirmishes continue along the Finnish front. The Red Army uses the lull to regroup and resupply, while Finnish troops take advantage of the break to fortify defensive positions and resupply frontline units. The Battle of Kelja commences between Finnish and Soviet forces. |
| Battle of the Atlantic: The Royal Navy continues patrols in the North Sea and the Atlantic, maintaining pressure on German naval forces. |
| Great Britain prepares for War: The British government finalises plans for further expanding aircraft production in 1940. |
| December 26th, 1939 |
| Winter War: The Soviet Union resumes full-scale attacks against Finnish positions, focusing on breaching the Mannerheim Line. Heavy casualties are reported on both sides as brutal trench warfare develops. |
| Battle of the Atlantic: German U-boats operate aggressively in the North Atlantic, sinking multiple Allied merchant ships. British escort vessels manage to destroy one U-boat, marking a small victory in the ongoing Battle of the Atlantic. |
| December 27th, 1939 |
| Winter War: The Battles of Kelja and Taipale conclude on this day, both ending in Finnish victories. Finnish forces launch counteroffensives against weakened Soviet positions near Tolvajärvi, forcing the Soviet Army units into retreat. Soviet military leaders, frustrated by repeated failures, seek new strategies to overcome Finnish defences. |
| Great Britain and France prepare for War: British and French high commands in France meet to discuss coordinated strategies for a potential German invasion in 1940. The British Expeditionary Force continues training along the Western Front. |
| December 28th, 1939 |
| Winter War: Soviet morale continues to decline as Finnish resistance proves unexpectedly effective. Reports emerge of Soviet soldiers suffering from frostbite and starvation due to supply shortages. |
| Battle of the Atlantic: The British Royal Navy expands its North Sea patrols, anticipating possible German naval operations against Scandinavia. |
| H.M.S. Barham Torpedoed: The German submarine U-30 torpedoes the British battleship H.M.S. Barham west of the Butt of Lewis in the Outer Hebrides. Four crew members are killed, but the H.M.S. Barham manages to return to Liverpool for six months of repairs. |
| British Food Rationing Announced: The British Minister of Food, W.S. Morrison, announces that starting January 8th, 1940, rationing will be expanded to include butter, bacon, ham, and sugar. |
| First Flight of the Consolidated XB-24 Liberator: The prototype of what will become the B-24 Liberator heavy bomber has its maiden flight at Lindbergh Field in San Diego, California. |
| December 29th, 1939 |
| Winter War: The Soviet Union again deploys additional reinforcements to the Finnish front, preparing for another large-scale assault in the new year. Stalin orders Soviet commanders to break Finnish resistance at any cost. |
| Great Britain prepares for War: British intelligence monitors German military build-ups along the western front, identifying increased troop concentrations near the Belgian border. |
| December 30th, 1939 |
| Winter War: In Finland, Finnish troops consolidate defensive positions and prepare for renewed Soviet offensives in the coming weeks. |
| Great Britain prepares for War: The Royal Air Force conducts another reconnaissance mission over Germany, gathering intelligence on key industrial sites producing war materials. |
| Great Britain and France prepare for War: British and French leaders discuss potential targets for future bombing campaigns. |
| Hermann Göring’s Warning: An article by Hermann Göring appeared in the Völkischer Beobachter, warning that once Hitler ordered the Luftwaffe to attack Britain, it would unleash an assault unprecedented in world history. |
| December 31st, 1939 |
| Winter War: The Finnish military achieves a significant victory by decimating the Soviet Union’s 163rd Infantry Division in central Finland. |
| Goebbels’ Address: German Propaganda Minister Joseph Goebbels delivers a radio address reviewing the events of 1939. He refrains from making predictions for 1940, stating that it “will be a hard year, and we must be ready for it.” |
| Subdued New Year’s Eve: Due to wartime blackout and noise restrictions, New Year’s Eve celebrations in Britain, France, and Germany ae notably restrained, with most festivities confined to private homes with shuttered windows. |