When Did World War II Start and End?

The official dates for World War II are September 1st, 1939, and September 2nd, 1945. However, several key dates are needed in order to understand the timeline in more detail.

Nov 14, 2023By Matt Whittaker, BA History & Asian Studies


On September 1st, 1939, the German Wehrmacht stormed across the Polish border, beginning World War II. This total war encompassed every continent, killing millions. The War ended six years later, on September 2nd, 1945, with Imperial Japan’s surrender. The war resulted from political tensions between Germany, France, Italy, and Great Britain throughout the 1930s. In Asia, Japan invaded China in 1937. Japan also looked towards the Pacific and Southeast Asia, hoping to solve its oil and raw material problems. The United States, the other significant power, grew nervous at Japan’s expansion via war.


Japanese troops march into China in 1939
Japanese troops march into China in 1939


European tensions peaked in September 1938 with the Munich Agreement. To appease Hitler and avoid war, Britain and France agreed that Czechoslovakia would cede territory with German minorities. Hitler still invaded Poland, and the Allies declared war.


As a result of Japan’s war with China, the U.S. imposed sanctions on Japan, specifically oil and scrap metal. As a resource-poor country, Japan’s options were limited. European colonies like the Dutch East Indies had the needed oil. In 1939, The Japanese government began war plans to obtain the required resources. In 1941, they went to war.


America Entered into World War II on December 7th

Pearl Harbor after the Attack. Source: National Archives and Records Administration
Pearl Harbor after the Attack. Source: National Archives and Records Administration


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The United States joined the war on December 8th, 1941. In 1939, America declared its neutrality, being reluctant to fight another war. Isolationism ruled the day right up to 1941. That ended with the Japanese attack on December 7th, 1941. The aerial attack, carefully planned by the Imperial Navy’s top commander, Admiral Yamamoto, aimed to destroy the U.S. Navy’s aircraft carriers. The carriers were out to sea, leaving only battleships. Four of the eight battleships were sunk, with 2,400 Americans dying. 


America declared war the next day as Roosevelt stood in front of a joint Congress. On December 11th, Germany declared war, reciprocated by the U.S. on the same day. The attack ended isolationism, galvanizing America to re-arm and millions to enlist. By 1945, America’s mood changed, and the country became a founding member of the United Nations.


Dates that Marked Pivotal Changes

German soldiers in Stalingrad. Source: Bundesarchiv
German soldiers in Stalingrad. Source: Bundesarchiv


Two dates marked crucial defeats for Germany and Japan. The Battle of Midway turned the tide against Japan, ending on June 7th, 1942. Following Pearl Harbor, Japanese forces ran roughshod over Asia, invading the Philippines, Hong Kong, and Singapore. Before this battle, Japan suffered a minor setback at the Coral Sea – Japan’s First Defeat.


Japan desired to establish a base on Midway to prevent attacks. The Imperial Navy assembled its fleet, including four aircraft carriers. Secretly, the U.S. Navy had cracked Japan’s radio codes, and they knew about the upcoming attack. In a three-day, mostly aerial duel, Japan lost three carriers rapidly when caught unprepared by American dive bombers. The fourth carrier, the Hiryu, sank after an intense air attack. The Americans lost the carrier Yorktown but withdrew because of superior Japanese numbers, particularly in battleships. The Battle of Midway checked Japan’s winning streak almost six months to the day after the Pearl Harbor attack. Subsequently, Japan lost momentum as America produced ships, planes, and tanks that Japan couldn’t match. 


Germany’s checkmate came on February 7th, 1943, with their 6th Army’s surrender, signaling the end of the Battle of Stalingrad. The battle began with promise as the Wehrmacht captured half the city, inflicting massive casualties, but they underestimated the Soviet’s determination – The Little Known Ally


Neither dictator could bear the thought of defeat, more so Stalin, as the city took his name. Dubbed “Rats War,” the Soviets and Wehrmacht fought bitterly in Stalingrad cellars and sewers. But a surprise Soviet pincer offensive cut the Germans off and into a starving siege. Barely 91,000 German soldiers remained to surrender from an army of 250,000. Only 5,000 ever returned home. Stalingrad destroyed Germany’s offensive capability in the East. Unable to replace the losses, the Germans, like their allies, never recovered. The Red Army ground its way west, concluding the war by capturing Berlin.


The Japanese Surrender of September 2nd, 1945

President Truman announces Japan’s surrender in the Oval Office. Source: National Archives
President Truman announces Japan’s surrender in the Oval Office. Source: National Archives


Imperial Japan capitulated to the Allies on this date in Tokyo Bay. But, hostilities ended on August 15th, 1945. The atomic bombings of Hiroshima and Nagasaki on August 4th and 6th forced a realization the Allies could now destroy entire cities. The ultra-secret American atomic weapons effort, The Manhattan Project, paid off, saving thousands of lives. On August 14th, Emperor Hirohito’s radio broadcast announced the acceptance of unconditional surrender. All fighting ceased at midnight on August 15th. The official surrender and document signing occurred on the battleship Missouri two weeks later, thus ending six years of costly war.

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By Matt WhittakerBA History & Asian StudiesMatt Whittaker is an avid history reader, fascinated by the why, how and when. With a B.A. in History and Asian Studies from University of Massachusetts, he does deep dives into medieval, Asian and military history. Matt’s other passion besides family is the long-distance Zen-like runs.