Written by Lauren Ko The Start and End of World War II World War II officially started on September 1st, 1939 and ended on September 2nd, 1945. Lasting six years and one day, World War II caused catastrophic damage. The war officially started in 1939, after Germany invaded Poland, causing the Allies (the U.K., France, Canada and others) to declare war on Germany and the Axis powers (Italy and Japan). The war ended after Adolf Hitler committed suicide on April 30, 1945 and a