Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity. A region named Germania was documented before AD 100. In 962, the Kingdom of Germany formed the bulk of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation.
Following the Napoleonic Wars and the dissolution of the Holy Roman Empire in 1806, the German Confederation was formed in 1815. Formal unification of Germany into the modern nation-state was commenced on 18 August 1866 with the North German Confederation Treaty establishing the Prussia-led North German Confederation later transformed in 1871 into the German Empire.
After World War I and the German Revolution of 1918–1919, the Empire was in turn transformed into the semi-presidential Weimar Republic. The Nazi seizure of power in 1933 led to the establishment of a totalitarian dictatorship, and World War II.