1939:
- September 1: Germany invaded Poland, marking the start of World War II.
- September 3: Britain and France declared war on Germany.
- The Soviet Union invaded eastern Poland on September 17, annexing the territories under the Molotov-Ribbentrop Pact.
1940:
- Nazi Germany invaded Denmark and Norway in April.
- The German Wehrmacht invaded Belgium, the Netherlands, and France in May, leading to the fall of France in June.
- The Battle of Britain began in July as the German Luftwaffe attempted to gain air superiority over the United Kingdom.
- Italy invaded Greece in October.
1941:
- Germany invaded the Soviet Union in June, launching Operation Barbarossa. This marked the opening of the Eastern Front, which would become the largest land theater of operations in history.
- Japan attacked Pearl Harbor and the United States entered the war on the side of the Allies.
- The United States, Britain, and the Soviet Union formed the Grand Alliance to fight against the Axis powers.
1942:
- Japan expanded its conquests in Southeast Asia, capturing Singapore, the Philippines, and Burma.
- The Battle of Midway in June was a turning point in the Pacific theater as the United States Navy dealt a severe blow to the Japanese fleet.
- The Battle of Stalingrad began in July and lasted until February 1943. It was a major victory for the Soviet Union, marking a significant turning point in the Eastern Front.
1943:
- The Allies began the strategic bombing campaign against Germany known as Operation Overlord.
- The Allies invaded Sicily and mainland Italy in July.
- The Soviet Union recaptured Kiev in November.
1944:
- The Allies liberated Rome in June.
- D-Day: The Allied forces invaded Normandy, France, on June 6, opening a second front against Germany.
- The Soviet Union launched a massive offensive against Germany in the summer, pushing them back to the borders of Germany itself.
1945:
- The Battle of the Bulge, the last major German offensive, took place in December 1944 and January 1945.
- Allied forces continued their advance into Germany, capturing key cities such as Cologne, Hamburg, and Dresden.
- The Soviet Union captured Berlin in April, and Adolf Hitler committed suicide.
- The German forces surrendered unconditionally on May 8, marking the end of the war in Europe.
- The United States dropped atomic bombs on Hiroshima and Nagasaki in August, leading to Japan's surrender and the end of World War II on September 2, 1945.
These are just some of the major historical events that occurred between 1939 and 1945. This was a period of immense conflict and upheaval, reshaping the geopolitical landscape and leaving a lasting impact on the world.