History

Key Decisions of WWII

Name: Key Decisions of WWII
Creator: Wikipedia / Imperial War Museum
License: https://creativecommons.org/licenses/by/4.0/

Which decision of World War II most altered the course of the conflict?

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Source:Wikipedia / Imperial War Museum

Updated:4/9/2026

#history #world war 2 #wwii #20th century #war

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Decision↕	Year↕	Decision Maker↕	Country↕	Theater↕	Outcome↕
Invasion of Poland	1939	Adolf Hitler	Germany	Europe	Triggered outbreak of World War II
Dunkirk evacuation	1940	Winston Churchill	United Kingdom	Europe	Saved 338,000 Allied troops from capture
Battle of Britain air defense	1940	Hugh Dowding	United Kingdom	Europe	First major defeat for Luftwaffe, invasion postponed
Operation Barbarossa	1941	Adolf Hitler	Germany	Eastern Front	Largest invasion in history, eventually failed
Attack on Pearl Harbor	1941	Hideki Tojo / Isoroku Yamamoto	Japan	Pacific	Brought United States into the war
Declaration of war on United States	1941	Adolf Hitler	Germany	Global	Linked European and Pacific wars
Wannsee Conference and Final Solution	1942	Reinhard Heydrich	Germany	Europe	Formalized genocide of European Jews
Battle of Midway trap	1942	Chester Nimitz	United States	Pacific	Four Japanese carriers sunk, turning point in Pacific
Defense of Stalingrad	1942	Joseph Stalin	Soviet Union	Eastern Front	German 6th Army destroyed, eastern turning point
Operation Overlord (D-Day)	1944	Dwight D. Eisenhower	United States / Allies	Europe	Opened Western Front in France
Operation Bagration	1944	Joseph Stalin / Stavka	Soviet Union	Eastern Front	Destroyed German Army Group Center
Battle of Leyte Gulf	1944	Douglas MacArthur	United States	Pacific	Largest naval battle in history, Japan's navy crippled
Yalta Conference agreements	1945	Roosevelt, Churchill, Stalin	Allies	Global	Shaped postwar Europe and Cold War borders
Atomic bombing of Hiroshima	1945	Harry S. Truman	United States	Pacific	First nuclear weapon used in war
Atomic bombing of Nagasaki	1945	Harry S. Truman	United States	Pacific	Second nuclear strike, Japan surrendered days later
Soviet declaration of war on Japan	1945	Joseph Stalin	Soviet Union	Pacific	Manchuria invaded, pressured Japanese surrender