In the aftermath of World War I, Austria-Hungary and the German Empire were partitioned, resulting in many Germans becoming ethnic minorities in newly established countries. In the chaotic years that followed, Adolf Hitler became the dictator of Nazi Germany and embarked on an genocidal campaign to unify all Germans under his leadership. This campaign resulted in World War II and the Holocaust. In the aftermath of Germany's defeat in the war, the country was occupied and partitioned, while millions of Germans were expelled from Eastern Europe. In 1990, the states of West and East Germany were reunified. In modern times, remembrance of the Holocaust has become an integral part of German identity ("Erinnerungskultur").