Before the War Why did the Second World War start? When did World War 2 begin? When did World War 2 end? In 1933 the German people voted for a leader named Adolf Hitler. Germany had been defeated in World War l (1914-1918) and Hitler promised to make his country great again. When did World War Two begin? World War Two in Europe began on 3rd September 1939, when the Prime Minister of Britain, Neville Chamberlain, declared war on Germany. It involved many of the world's countries. Why did the Second World War start? Germany took over Austria and Sudetenland (a region in Czechoslovakia) before the war and was soon threatening the rest of Europe too. The Second World War was started by Germany in an unprovoked attack on Poland. Britain and France declared war on Germany after Hitler had refused to abort his invasion of Poland. When did World War Two end? The War ended in the 14 August 1945. It is estimated that 50 million people lost their lives during World War 2.