The result of the Franco-Prussian War, with Prussia defeating France, paved the way for the unification of all the German states under Prussian leadership. The work, which the Parliament of Frankfort had failed to carry out in the revolutionary period, was easily accomplished at a time when Germans were fighting side by side for a common Fatherland. Bismarck, prime minister under William I of Prussia, was enabled to sweep away the unnatural line of the Main, and to extend the Northern German Confederation of 1867 over the four states of southern Germany.
The terms of union were settled in separate negotiations with the governments of Bavaria, Wurtemberg, Baden, and Grand ducal of Hesse. They were then submitted for formal approval to the estates of each province and to the diet of the North German Confederation, On January 18, 1871, the veteran King of Prussia was formally proclaimed German Emperor in the great Hall of Mirrors at Versailles, at the end of the Franco-Prussian War. Otto von Bismarck was appointed Imperial Chancellor.
The unification of Germany allowed this country to exert its political and economical hegemony in continental Europe and rivaled with Great Britain in colonial territorial gains in the Second Industrial Revolution context. It revived in Germany a national unity and nationalistic sentiment that had perished six centuries before. The German Empire was acknowledged since 1871 to be the first military power in Europe as the national pride in this position made the people overlook many domestic inconveniences and even humiliations. Bismarck were able to maintain the ascendancy of Prussia in spite of serious quarrels with the Roman Catholic clergy, and in spite of the threatening attitude of social democracy.