Simplify the following text for a Grade 9 native English-speaking person.
Original: The formal unification of Germany into a politically and administratively integrated nation state officially occurred on 18 January 1871 at the Versailles Palace 's Hall of Mirrors in France .
Simplified: Unification took place on 18 January 1871 . At the conclusion of the Franco-Prussian War , the German princes proclaimed the German nation in Versailles , France , at the Hall of Mirrors .