World War 2 began with the rise of Adolf Hitler and the Nazi party in Germany in the 1930s. Hitler gained power as Chancellor in 1933 and established a fascist dictatorship. Germany invaded Poland in 1939, which led Britain and France to declare war on Germany. Germany then conquered much of continental Europe. The Holocaust led to the genocide of approximately 6 million Jews and other groups deemed undesirable by the Nazis. Allied forces turned the tide starting in 1942-1943, leading to the eventual defeat of Germany in 1945.