World War II (1 September 1939–2 September 1945) was a global war between the and the .

Context: World War II as a global coalition conflict; identifying belligerents

Historians disagree on when the war truly began; one common anchor is the 1 September 1939 invasion of .

Context: Competing start-date interpretations; recognizing the common anchor

Post–World War I instability and the Treaty of Versailles contributed to nationalism and political instability, especially in Germany.

Context: Post–World War I instability and revisionist nationalism

was a policy of avoiding confrontation with aggressive powers, which reduced opposition to some German actions.

Context: Appeasement

The Molotov–Ribbentrop Pact partitioned Poland between Germany and the .

Context: Molotov–Ribbentrop Pact; avoiding a common confusion about who partitioned Poland

Japan established the puppet state of after the Mukden incident.

Context: Pre-war events in Asia; Manchukuo

Germany and Japan signed the Pact in 1936, aiming to counter the Communist International.

Context: Anti-Comintern Pact

Nazi Germany invaded Poland on 1 September 1939; this caused the UK and France to declare war on Germany two days later, expanding the conflict in .

Context: Cause→effect chain; invasion triggers declarations and European expansion

Germany invaded the Soviet Union in June 1941; this opened the Front as a major theater of fighting.

Context: Cause→effect chain; Eastern Front opening

Japan attacked American and British territories in December 1941, including Pearl Harbor; this caused the to enter the war against the Axis.

Context: Cause→effect chain; Pacific War escalation after Japan’s attacks

Japan’s advances in the Pacific were halted in June 1942 at the .

Context: Battle of Midway; identifying a major turning point

Axis forces were defeated in North Africa and at Stalingrad in early 1943; this weakened Axis momentum and gave the Allies more leverage across multiple .

Context: Cause→effect chain; defeats lead to Allied leverage across multiple fronts

The US dropped atomic bombs on Hiroshima and Nagasaki; combined with Soviet invasion of Japanese-occupied Manchuria, this caused Japan to announce surrender on 15 August 1945.

Context: Cause→effect chain; atomic bombs and surrender type

Japan announced unconditional surrender on 15 August 1945 ( Day), but the formal end in Asia came when Japan signed the surrender document on 2 September 1945.

Context: V-J Day vs formal surrender; avoiding the end-date confusion

After victory, the UN was created to foster cooperation and prevent future conflicts, and US–Soviet rivalry set the stage for the .

Context: War termination and postwar consequences; Cold War foundations