World War II Dates: The Complete Chronology From September 1939 To September 1945

The Second World War unfolded across six relentless years, from the invasion of Poland on 1 September 1939 to the formal surrender of Japan on 2 September 1945. This global conflict redrew the map of the world, reshaped international institutions, and set the stage for the Cold War, all through a sequence of decisive dates and turning points. The following timeline traces the major political, military, and diplomatic milestones that defined the war from its outbreak to its conclusion.

1939: The Collapse of Appeasement

In the late 1930s, European leaders pursued a policy of appeasement, hoping to satisfy Adolf Hitler’s demands and avoid another continental war. That strategy collapsed in the summer of 1939 as Nazi Germany and the Soviet Union signed a non-aggression pact with secret protocols dividing Eastern Europe into spheres of influence. The stage was set when Germany invaded Poland on 1 September 1939, prompting Britain and France to declare war two days later on 3 September 1939. The Soviet Union followed on 17 September 1939, invading Poland from the east and completing its partition.

• 1 September 1939: Germany invades Poland, initiating World War II in Europe.
• 3 September 1939: Britain and France declare war on Germany.
• 17 September 1939: The Soviet Union enters Poland, beginning its eastern campaign.
• 6 October 1939: Poland is effectively divided between Germany and the Soviet Union.

During what historians call the “Phoney War,” little fighting occurred on the Western Front, but diplomatic efforts to deter Hitler failed. As the winter of 1939–1940 settled over Europe, the focus shifted to Scandinavia, where Germany launched Operation Weserübung on 9 April 1940, invading Denmark and Norway to secure iron ore shipments and protect its northern flank.

1940: The Fall Of France And The Battle Of Britain

The spring of 1940 marked a dramatic escalation in the war. On 10 May 1940, Germany launched its blitzkrieg into Belgium, the Netherlands, and Luxembourg, bypassing the Maginot Line and thrusting deep into France. By 28 May 1940, Belgian forces surrendered, and the evacuation of Allied troops from Dunkirk began on 26 May 1940, concluding on 4 June 1940 with the rescue of hundreds of thousands of soldiers.

The fall of France was swift and humiliating. On 22 June 1940, an armistice was signed in Compiègne, dividing France into occupied and Vichy-controlled zones. With Britain standing alone, Adolf Hitler issued Führerbefehl No. 16 on 16 July 1940, ordering preparations for Operation Sea Lion, the invasion of Britain. The ensuing Battle of Britain raged through the summer and autumn, climaxing with the Luftwaffe’s concentrated raids in August and September. The turning point came on 15 September 1940, celebrated as Battle of Britain Day, when the Royal Air Force decisively repelled a massive German air attack, forcing Hitler to indefinitely postpone the invasion.

• 10 May 1940: Germany launches offensive in the West.
• 28 May 1940: Belgium surrenders.
• 22 June 1940: Armistice between France and Germany signed.
• 10 July – 31 October 1940: The Battle of Britain.
• 15 September 1940: RAF victory over the Luftwaffe, Battle of Britain Day.

1941: Global War Erupts

While Europe burned, Asia simmered. Japan had been at war with China since 1937, but the conflict exploded globally on 7 December 1941 when Japanese forces launched a surprise attack on the U.S. naval base at Pearl Harbor. The following day, 8 December 1941, the United States declared war on Japan. Germany and Italy responded by declaring war on the United States on 11 December 1941, transforming the regional conflict into a truly global war.

In the east, Hitler turned his attention to the Soviet Union. Operation Barbarossa, the invasion of the USSR, began on 22 June 1941, shattering the non-aggression pact and opening the largest theater of war in history. The early months saw devastating losses for the Soviets, but the vastness of Russian territory and the onset of winter halted the German advance just short of Moscow in December 1941.

• 22 June 1941: Operation Barbarossa, the invasion of the Soviet Union, begins.
• 7 December 1941: Attack on Pearl Harbor.
• 8 December 1941: United States declares war on Japan.
• 11 December 1941: Germany and Italy declare war on the United States.
• 7–16 December 1941: Battle of Hong Kong and Japanese advances in Southeast Asia.

1942: The Turning Point Begins

1942 was the year the tide began to turn. In the Pacific, the Battle of Midway from 4 to 7 June 1942 crippled the Japanese fleet, destroying four aircraft carriers and shifting naval dominance to the Allies. In North Africa, the Second Battle of El Alamein, which ended in early November 1942, halted the Axis advance toward the Suez Canal. The war on the Eastern Front reached a critical juncture with the Soviet victory at Stalingrad, which ended in February 1943 after months of brutal urban warfare that had begun with the German summer offensive on 28 June 1942.

• 4–7 June 1942: Battle of Midway.
• 23 October – 11 November 1942: Second Battle of El Alamein.
• 28 June 1942 – 2 February 1943: Battle of Stalingrad.

These victories marked a fundamental shift in momentum. As General Bernard Montgomery famously remarked after El Alamein, “Now this is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.”

1943–1944: Advance And Liberation

The Allies spent 1943 methodically pushing back their enemies. In July 1943, Allied forces invaded Sicily, leading to the fall of Mussolini on 25 July and Italy’s surrender on 8 September, though fighting continued on the Italian peninsula for nearly another year. On the Eastern Front, Soviet forces launched a massive counteroffensive at Kursk in July–August 1943, the largest tank battle in history, which exhausted German offensive capabilities. The Red Army began a relentless westward push in 1944.

In the west, the long-awaited invasion of France, codenamed Operation Overlord, commenced on D-Day, 6 June 1944. The successful landings in Normandy established a critical second front. As the Soviets advanced from the east, the Allies closed in on Germany from both sides. The liberation of Paris occurred in August 1944, and the Allies reached Germany’s western border by the end of the year.

• 9 July 1943: Allied invasion of Sicily.
• 25 July 1943: Mussolini deposed.
• 6 June 1944: D-Day landings in Normandy.
• 25 August 1944: Liberation of Paris.
• 7 December 1944: Battle of the Bulge begins.

1945: Victory And Surrender

The final year of the war was marked by swift collapse and ultimate tragedy. Soviet forces entered Poland in January 1945 and captured Berlin in April. Hitler died by suicide in his bunker on 30 April 1945. Germany formally surrendered unconditionally to the Allied forces on 7 May 1945, a date that was ratified the following day, 8 May 1945, now celebrated as Victory in Europe (V-E) Day.

The war against Japan continued for four more months. The United States ended the conflict by dropping atomic bombs on Hiroshima on 6 August 1945 and Nagasaki on 9 August 1945. Facing imminent invasion and the unprecedented destruction of the atomic bombs, Japan offered to surrender on 10 August 1945. The formal surrender ceremony took place on the deck of the USS Missouri in Tokyo Bay on 2 September 1945, finally bringing World War II to its definitive close.

• 30 April 1945: Adolf Hitler dies.
• 7 May 1945: German surrender signed at Reims.
• 8 May 1945: V-E Day.
• 6 August 1945: Atomic bomb dropped on Hiroshima.
• 9 August 1945: Atomic bomb dropped on Nagasaki.
• 2 September 1945: Formal Japanese surrender aboard the USS Missouri, marking V-J Day.

The precise sequence of these dates—1 September 1939 to 2 September 1945—captures the arc of a world consumed by conflict and the enduring legacy of a war that reshaped the human experience.