This is a timeline on some major events during World War II. World War II timeline suggests how the biggest war of this generation started and ended. Lasting six years and one day, the Second World War started on 1 September 1939 with Hitler's invasion of Poland and ended with the Japanese surrender on 2 September 1945. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe and formed the Axis alliance with Italy and Japan. As the timeline diagram illustrates, in December 1941, Japan attacked American and British territories with near-simultaneous offensives against Southeast Asia and the Central Pacific, including an attack on the US fleet at Pearl Harbor which forced the US to declare war against Japan.