September 1939

September 2nd, 1939
Fall Weiß: German forces continue their rapid advance, capturing Częstochowa and pushing towards Łódź. The Luftwaffe intensifies its bombing campaign, targeting Warsaw, Kraków, and other key cities.
Poland Defends: The Polish 7th Infantry Division attempts to slow the German advance near Tomaszów Mazowiecki but suffers heavy casualties. The Polish Army Kraków begins a retreat towards the Dunajec River to avoid encirclement.
International Responses: Italy proposes a peace conference to address the crisis, aiming to prevent a broader conflict. Meanwhile, Ireland declares its neutrality, choosing to remain uninvolved in the escalating war.
International Responses: Great Britain and France deliver an ultimatum to Germany, demanding an immediate cessation of hostilities and withdrawal from Poland. Hitler refuses to comply.
Second Sino-Japanese War: Japanese forces conduct bombing raids on Chongqing, China, intensifying their campaign in the region.

September 3rd, 1939
Declaration of War: At 11:00 British Summer Time, Great Britain declares war on Germany, followed shortly by France. The British Expeditionary Force begins mobilisation for deployment to France. Australia and New Zealand also declare war on Germany.
SS Athenia Sunk: The British passenger liner SS Athenia is torpedoed by the German submarine U-30, killing 112 civilians. This attack marks the first British ship sunk by the Kriegsmarine in World War II and leads to international outrage.
Fall Weiß: German forces continue advancing, with the 10. Armee crossing the Pilica River and pushing towards Warsaw.
Poland Defends: The Polish Army Łódź attempts a defensive stand but is overwhelmed by mechanised German forces. Polish forces reinforce defensive positions around the capital in preparation for a siege.
Second Sino-Japanese War: Japanese forces continue their campaign in central China, launching coordinated assaults on Nationalist positions in Sichuan Province.

September 4th, 1939

British Air Raid: The Royal Air Force launches its first bombing raid of the war, targeting German naval facilities at Wilhelmshaven with limited success. The raid marks the beginning of Britain’s offensive operations against Germany.

Polish Retreat: The Polish Army Pomorze, heavily engaged in northern Poland, is now nearly encircled. The Polish Army Kraków retreats towards the Vistula River, attempting to form a new defensive line. The Polish destroyers ORP Błyskawica, ORP Grom, and ORP Burza escape from the Baltic Sea and sail to Britain to avoid destruction by the Kriegsmarine.

South Africa Enters the War: South Africa declares war on Germany, aligning with the Allies. This decision reflects the country’s ties to Britain and its commitment to opposing German aggression.

September 5th, 1939

Declaration of Neutrality: President Franklin D. Roosevelt proclaims U.S. neutrality in the European conflict, reflecting the nation’s desire to avoid entanglement in foreign wars.

Fall Weiß: The German 14. Armee captures Kraków. German forces reach the outskirts of Warsaw. The Luftwaffe increases its bombing raids, striking major railway junctions to prevent Polish reinforcements from reaching the capital.

Polish Retreat: Polish troops begin withdrawal to the Romanian Bridgehead. The Polish government evacuates to Lublin as German forces press further eastward.

Second Sino-Japanese War: Japanese forces advance deeper into Hubei Province, pressing Nationalist forces towards the interior.

September 6th, 1939

Fall Weiß: German troops capture Kraków as they push deeper into Polish territory. Polish defences continue to collapse.

Polish Regroup: Polish forces attempt to consolidate defensive lines along the Vistula River. The Polish High Command orders all available units to regroup east of the Vistula.

British Blockade: The British Royal Navy enforces a naval blockade on Germany to restrict its trade and supply lines.

September 7th, 1939

French Saar Offensive: The French Army initiates a limited offensive into the German Saar region, aiming to divert German forces from Poland. However, the French forces in the Saarland continue their slow, cautious advance, avoiding major engagements with the German defenders. The operation lacks decisive action and fails to significantly impact German military deployments.

Polish Troops Surrender: After a week of intense fighting, the Polish garrison, at Westerplatte in the free city of Danzig, surrenders to German forces. The defenders, numbering fewer than 200 men, have held out against repeated German assaults, artillery bombardments, and Luftwaffe air raids for 1 week.

Warsaw Siege: German forces near Warsaw begin preparations for an assault on the city, encircling Polish defenders and cutting off supply lines. The Polish Army, realising the vulnerability of the capital, attempts to establish stronger defensive positions around the city.

Soviet Union prepares for War: Soviet intelligence continues monitoring German military movements, preparing for potential intervention in Poland.

Second Sino-Japanese War: Japanese forces increase their offensive efforts in central China, launching fresh attacks on Nationalist positions in the Hubei and Hunan provinces.

September 8th, 1939

Siege of Warsaw Begins: The German 4. Panzer-Division reaches Warsaw’s western suburbs and launches an initial assault, but Polish defenders successfully repel the attack. Polish forces prepare a counteroffensive along the Bzura River to relieve pressure on the capital. The Luftwaffe escalates its bombing campaign against Warsaw. The Luftwaffe intensifies bombing raids over Warsaw, targeting key infrastructure, communication lines, and residential areas. Civilians begin evacuating where possible, while others join the city’s defence efforts.

Poland Defends: Polish forces attempt to organise a counteroffensive along the Bzura River to relieve pressure on the capital.

French Saar Offensive: French troops in the Saarland probe deeper into German defences but remain hesitant to engage in full-scale combat.

Second Sino-Japanese War: Japanese naval forces tighten their blockade of Chinese supply lines, aiming to weaken Nationalist resistance.

September 9th, 1939

Battle of Bzura: Polish forces under General Tadeusz Kutrzeba launch the Battle of the Bzura, the largest Polish counterattack of the campaign. Polish infantry, supported by cavalry and light artillery, successfully pushes back German positions along the river. Forcing the German 8. Armee to retreat temporarily. However, the Luftwaffe quickly intervenes, launching continuous air strikes against Polish positions. Despite initial successes, Polish forces find themselves increasingly vulnerable to German air superiority.

Siege of Warsaw Begins: Polish troops continue repelling German advances, inflicting heavy casualties in house-to-house fighting. German artillery bombardments increase in intensity, setting parts of the city ablaze.

Soviet Union prepares for War: Stalin monitors the progress of the German invasion closely, awaiting the right moment to intervene in Poland as per the secret agreements of the Molotov-Ribbentrop Pact.

Second Sino-Japanese War: Japanese forces launch another wave of air raids on Chongqing, China.

September 10th, 1939

Declaration of War: Canada enters the war, standing with Britain and France against Germany. This marks a significant commitment of Canadian military resources to the Allied cause.

Battle of Bzura: Polish forces at the Bzura River continue their counteroffensive, inflicting significant losses on German forces. The Polish Army manages to recapture several towns and temporarily disrupts German supply lines. However, German reinforcements, including additional Panzer divisions and Luftwaffe air support, begin arriving, gradually turning the tide of the battle.

Siege of Warsaw: The German 10. Armee continues its encirclement of Warsaw, cutting off Polish supply routes. The Polish Army Modlin reinforces defensive positions around the city. Civilian casualties mount as German bombardments intensify. The Polish government remains in the capital, refusing to surrender despite the worsening situation.

September 11th, 1939

Saudi Arabia Severs Ties: Saudi Arabia breaks off diplomatic relations with Germany, signaling its disapproval of German aggression and aligning more closely with the Allied powers.

Battle of Bzura: The Battle of the Bzura intensifies, with heavy casualties on both sides.

Siege of Warsaw: The German 10. Armee tightens its grip around Warsaw, while Polish forces attempt to break out. Polish forces defending the city construct barricades and prepare for prolonged urban combat.

German Advance: The German 10. Armee strengthens its grip on central Poland, surrounding multiple Polish divisions.

Saar Offensive: In the west, the French Saar Offensive loses momentum as French forces halt their advance.

September 12th, 1939

Allied War Council: The Anglo-French Supreme War Council convenes Abbeville, France, to coordinate military strategies, reflecting the need for unified planning in response to German offensives. Discussions focus on potential actions to relieve pressure on Poland and prepare for broader conflict. France, deciding against launching a full-scale offensive in support of Poland. This marks the failure of Allied military intervention in the campaign.

Battle of Bzura: The Battle of the Bzura reaches a critical phase as German forces encircle Polish troops attempting to advance. Heavy aerial bombardments and armoured counterattacks force Polish units into a defensive stance.

Siege of Warsaw: Warsaw remains under heavy artillery and aerial bombardment.

September 13th, 1939

Battle of Modlin: German forces engage Polish defenders at Modlin Fortress, a strategic stronghold near Warsaw. The prolonged siege tests the resolve of Polish troops and becomes a symbol of resistance.

Siege of Warsaw: Warsaw is now completely encircled. The Luftwaffe carries out sustained bombing raids, devastating infrastructure and morale.

Lwów Assault: Polish troops in Lwów prepare for defence as German forces approach.

September 14th, 1939

Soviet-Japanese Ceasefire: The Battles of Khalkhin Gol between the Soviet Union and Japan conclude with a ceasefire. The agreement eases tensions in the Far East, allowing the Soviet Union to focus more attention on developments in Europe.

Fall Weiß: The German 19. Panzer-Korps crosses the Bug River, cutting off Polish units attempting to retreat eastward. The Wehrmacht seizes control of Brest-Litovsk, an important stronghold in eastern Poland. The Polish Army, already overstretched, struggles to maintain defensive lines in multiple locations.

Siege of Warsaw: Polish forces desperately hold defensive positions in Warsaw, facing continuous German artillery bombardment. Polish troops fighting in Warsaw receive diminishing supplies as German forces block escape routes.

Lwów Assault: In Lwów, Polish defenders reinforce their positions in anticipation of an imminent siege.

September 15th, 1939

Battle of Bzura: Polish forces at the Bzura River attempt a final breakout, hoping to link up with defenders in Warsaw. However, overwhelming German firepower, combined with continuous Luftwaffe strikes, decimates Polish troops. The remnants of the Polish counteroffensive begin retreating towards the east. Fighting continues along the Bzura River, with Polish forces attempting to break through German lines.

Siege of Warsaw: The Luftwaffe launches heavy air raids on Warsaw, crippling the city’s supply routes. German forces tighten their encirclement around the city, making Polish counteroffensives increasingly difficult.

Soviet Preperations: In the east, Soviet forces continue their preparations for intervention.

September 16th, 1939

Siege of Warsaw: Warsaw remains under heavy bombardment, with German forces preparing for an all-out assault on the city. The Luftwaffe carries out its heaviest bombing raid yet, reducing large sections of Warsaw to rubble. Civilian casualties rise dramatically, and Polish resistance forces struggle to maintain morale. Warsaw remains under relentless attack as German troops probe the city’s defences. Polish forces desperately hold their defensive positions.

Lwów Attack: In the south, Polish troops in Lwów launch a counterattack against advancing German forces but struggle to maintain their positions due to dwindling supplies. Polish forces desperately hold their defensive positions.

Fall Weiß: The German 19. Panzer-Korps crosses the Bug River, cutting off Polish units attempting to retreat eastward.

Germany and Soviet Union prepare to become Allies: German and Soviet diplomats continue back-channel negotiations for the division of Poland, as outlined in the secret protocol of the Molotov-Ribbentrop Pact. The Red Army readies itself for intervention, awaiting the final order from Stalin.

September 17th, 1939

Soviet Union invades Poland: At 03:00, the Soviet Union joins Germany and invades Poland from the east, following the terms of the Molotov-Ribbentrop Pact. Under the pretext of protecting ethnic Ukrainians and Belarusians. The Polish government, already under immense pressure from the German invasion, orders its remaining forces not to engage the Soviets unless attacked. The invasion from the east effectively seals Poland’s fate, as Polish troops find themselves surrounded on both fronts.

Siege of Warsaw: German forces prepare for a final push into the city, while Polish defenders continue to fortify their last strongholds.

Polish Government: The Polish government and military high command begin preparations to flee to Romania, hoping to establish a government-in-exile.

September 18th, 1939

Polish Government: The Polish government and military high command, realising the impossibility of continuing resistance against both Germany and the Soviet Union, flee into Romania. Despite their escape, the Polish government refuses to surrender and begins organising a government-in-exile from Paris. Polish military personnel also attempt to escape into Romania and Hungary, with plans to regroup and continue the fight from France and Britain.

German and Soviet Advance: German forces advance further east, capturing Brest-Litovsk. There, German and Soviet forces conduct their first coordinated movements, following the secret agreements of the Molotov-Ribbentrop Pact. The Soviet Army advances rapidly, meeting little resistance from Polish forces, many of whom attempt to retreat or surrender to avoid encirclement.

Siege of Warsaw: Food and ammunition supplies dwindle as German artillery and Luftwaffe bombardments intensify. The Polish defenders brace for an inevitable final German assault.

Lwów Attack: The Luftwaffe continues bombing raids on Lwów, despite the Soviet advance.

Polish Retreat: The Polish submarine ORP Orzeł escapes internment in Estonia.

Second Sino-Japanese War: The Imperial Japanese Army continues its offensive in China, launching new attacks against Nationalist forces in Hunan and Sichuan provinces. Japanese naval forces conduct operations in the South China Sea to disrupt Chinese supply routes.

Soviet–Japanese Border Conflicts: The Soviet-Japanese conflict at Khalkhin Gol in Mongolia has now ended in a Soviet victory, with Japanese forces retreating after heavy losses.

September 19th,1939

Soviet Advance: Soviet forces advance deeper into eastern Poland, meeting little organised resistance. The Polish Army, already engaged in battles with the Germans, lacks the resources to counter the Soviet invasion. Some isolated Polish units engage Soviet forces but are quickly overwhelmed.

German and Soviet Armies Meet: The German and Soviet forces begin meeting in occupied Poland, coordinating their movements. In Brest-Litovsk, German and Soviet forces meet for the first time. German commanders hand over control of the city to the Soviets, as agreed in the Molotov-Ribbentrop Pact. Red Army troops take over administration, while Polish prisoners captured by both sides begin being processed for internment. Thousands of Polish officers are detained by Soviet forces, many of whom will later be executed in the Katyn Massacre.

Lwów Attack: The siege of Lwów intensifies as Soviet forces prepare for a full-scale assault. The Luftwaffe continues bombing raids on Lwów, despite the Soviet advance.

Polish resistance: Polish resistance fighters engage German units in isolated skirmishes, attempting to disrupt enemy supply lines.

Siege of Warsaw: Warsaw remains under constant bombardment, and morale within the city is low. The Polish military attempts to maintain order among civilians, but the effects of starvation and exhaustion take their toll.

Second Sino-Japanese War: Japanese forces intensify their campaign against Chinese guerrilla fighters. Air raids on Chongqing continue, causing heavy civilian casualties.

Great Britain prepares for War in the East: The British Royal Navy begins reinforcing its presence in Singapore in response to growing Japanese expansion.

September 20th, 1939

Battle of Bzura: The Battle of the Bzura officially ends in a German victory.

Polish Resistance Collapses: Polish resistance in eastern Poland continues to collapse as Soviet forces seize Lwów and Wilno. Many Polish troops attempt to retreat towards the Romanian and Hungarian borders, hoping to escape captivity.

Siege of Warsaw: German forces tighten their grip on Warsaw. The city’s defenders continue to hold, but with food and ammunition supplies critically low, their ability to resist is diminishing. The Luftwaffe conducts large-scale bombing raids on the city, causing severe civilian casualties and widespread destruction.

Fall Weiß: German forces continue their push towards eastern Poland, securing more territory as Polish resistance weakens.

Italy prepares for War: Italy continues its military build-up in Libya, preparing for possible hostilities against British and French interests in North Africa. The British Royal Navy monitors Italian naval movements in the region.

September 21st, 1939

Germany and Soviet Union meet: German and Soviet commanders meet in Brest-Litovsk to discuss the final partition of Poland.

Holocaust: Reinhard Heydrich, head of the SS Security Service, issues the “Resettlement Order,” marking the beginning of German plans to remove Jews and Polish elites from occupied territories. The first mass arrests begin in German-occupied Poland, with intellectuals, politicians, and community leaders among the primary targets.

Siege of Warsaw: Warsaw’s defences continue to hold despite relentless German attacks. The city is now fully surrounded, and no reinforcements or supplies can reach its defenders.

Second Sino-Japanese War: Japanese forces continue their encirclement of Chinese strongholds in Hunan and Guangxi provinces, pushing deeper into Nationalist territory.

Great Britain prepares for War in the East: The British government discusses defensive preparations in the Far East in response to Japanese expansion.

September 22nd, 1939

Soviet Advance: The Red Army enters Lwów after intense fighting. Polish defenders surrender after running out of ammunition and supplies. They also capture Wilno (Vilnius), effectively securing control over northeastern Poland.

Germany and Soviet Union celebrate their Alliance: In Brest-Litovsk, German and Soviet forces conduct a joint military parade, publicly showcasing their new alliance.

French Saar Offensive: French forces continue their limited operations in the Saarland but fail to make significant progress.

Great Britain prepares for War: The British Royal Navy strengthens its patrols in the Atlantic, preparing for the threat of German U-boat activity.

September 23rd, 1939

Siege of Warsaw: Warsaw remains under siege. The German Army launches another major assault on Warsaw, supported by heavy artillery and Luftwaffe bombing. The Polish defenders, exhausted and lacking supplies, continue to resist, engaging in fierce street fighting. Reports emerge of significant civilian casualties as German artillery fire indiscriminately strikes residential areas. Food shortages and infrastructure damage worsen conditions inside the city, with civilians suffering heavily.

Second Sino-Japanese War: Japanese forces intensify their blockade of Chinese ports, aiming to cut off foreign aid to the Chinese government.

Great Britain and France prepare for War in the Far East: The British and French discuss contingency plans for possible hostilities with Japan.

September 24th, 1939

Siege of Warsaw: The Luftwaffe carries out its heaviest bombing raid on Warsaw, dropping thousands of tons of explosives on the city. The attack devastates entire districts, setting fire to buildings and destroying key infrastructure.

Soviet Advance: The Soviet Union consolidates control over eastern Poland, establishing new administrative structures in occupied territories. Mass deportations of Polish citizens to Siberia and Central Asia begin under Soviet orders.

Japan prepares for War: Tensions rise as Japan increases its naval patrols near British and Dutch territories in Southeast Asia, prompting concerns in London and The Hague.

September 25th, 1939

Siege of Warsaw: Warsaw remains in flames following the devastating air raids. German artillery continues bombarding Warsaw. Polish officials inside the city realise that further resistance is unsustainable, as they are completely cut off with no reinforcements or supplies. German forces prepare for the final push into the city.

Battle of the Atlantic: German U-boats begin targeting Allied shipping, marking the early stages of the Battle of the Atlantic. The British Admiralty increases convoy protections and issues warnings to merchant vessels.

September 26th, 1939

Siege of Warsaw: Warsaw remains under siege, enduring continuous German bombardment. The Luftwaffe conducts its heaviest air raid, devastating the city. Warsaw’s leaders begin surrender negotiations with German commanders. Conditions inside the city are dire, with food and medical supplies nearly exhausted. The Polish defenders, though unwilling to capitulate, acknowledge that further resistance would lead to mass civilian casualties.

Italy prepares for War: Italian naval forces conduct further training exercises, signalling Mussolini’s increasing readiness for potential conflict. Britain and France closely monitor Italian movements, preparing for future developments.

September 27th, 1939

Warsaw Surrenders: Warsaw surrenders after nearly four weeks of intense resistance. The Polish Army lays down its arms, and German forces officially enter the city. German occupation forces quickly establish control, imposing martial law. Thousands of Polish soldiers and civilians are taken prisoner. Despite the surrender, isolated Polish units continue to resist in other parts of the country. Polish underground movements begin forming, determined to carry on the fight through resistance and sabotage.

Soviet Occupation: The Soviet Union consolidates its control over eastern Poland, disarming and capturing remaining Polish forces in the region.

Soviet Deportations: Stalin’s government begins political purges, deporting thousands of Polish officers, officials, and intellectuals to the Soviet interior.

Second Sino-Japanese War: Japanese forces continue their expansion in China, pressing towards crucial supply centres.

September 28th, 1939

Germany and Soviet Union become Allies: Germany and the Soviet Union sign the German-Soviet Boundary and Friendship Treaty, officially dividing Poland into their respective spheres of influence. The agreement formalises the partition, with Germany taking western Poland and the Soviet Union taking the east. Secret protocols dictate further cooperation in suppressing Polish resistance movements.

September 29th, 1939

Fall Weiß: German forces almost complete the occupation of western Poland, dismantling organised pockets of Polish resistance. The Wehrmacht begins consolidating its control, while SS units initiate mass arrests and executions of perceived enemies of the Reich.

Polish resistance: Organised Polish military resistance ceases. However, underground resistance groups begin forming in occupied areas. The exiled government aims to continue Polish resistance and maintain Polish sovereignty.

German U-boat campaign: German U-boat U-27, is sunk the previous day (September 29) by British destroyers H.M.S. Fortune and H.M.S. Forester west of the Hebrides.

September 30th, 1939

Polish Government: The Polish government-in-exile is formally established in Paris, led by General Władysław Sikorski. The exiled government declares its intent to continue the struggle against Germany, seeking support from Britain and France.

Polish Resistance: Underground resistance groups such as the Polish Home Army (Armia Krajowa) begin forming, laying the foundation for future resistance efforts against both German and Soviet occupiers.