For questions on German Empire, Weimar Republic, German Democratic Republic and the modern Federal Republic of Germany. Questions regarding the Third Reich should be tagged with Nazi-Germany.
The German Empire existed from 1871 to 1918 and was the result of a unification of German states largely driven forward by Prussia. After World War I a parliamentary republic replaced the monarchy. This so-called Weimar Republic existed from 1919 to 1933. After Adolf Hitler came to power in 1933 he gradually dismantled the republic, starting a period of German history called Third Reich. This period ended in 1945 with Germany's defeat in World War 2 and occupation by allied forces. In 1949, the British, American and French occupation zones merged into Federal Republic of Germany, a parliamentary republic, and the Soviet occupation zone became German Democratic Republic, a socialist republic. Germany was reunified in 1990 with the German Democratic Republic joining the Federal Republic of Germany.