Nazi Germany is one of three nations in Europe, since it invaded and occupied all European countries except Great Britain and its ally Italy. It succeeded the Weimar Republic as the government in Germany and vowed revenge upon the Allies for German defeat in World War I.
The Reich was bound on taking other nations for German glory. First, it annexed Austria. Then it took the Sudetenland in 1938. When Hitler proceeded to invade the rest of Czecholslovakia, war was declared. Eventually, Germany defeated Denmark, Holland, Belgium, Poland, Norway, Sweden, Yugoslavia, the Baltic states, the Balkan states, Spain, and France.
In the 40s, Hitler was killed during an air raid. Following his death, Heinrich Himmler became the Führer.
The Führer is the Chancellor of Germany, and basically has ultimate power in the Reich. The first was the infamous Adolf Hitler, succeeded by Reichsführer of the SS Heinrich Himmler.