1870, conflit franco-prussien
19th July 1870: France declares war on Prussia.
Early August 1870: beaten in Alsace and Lorraine, the main French army is encircled in Metz.
23rd August 1870: under the command of Mac Mahon, the Army of Châlons takes the road for the Ardennes. After a series of exhausting marches and counter-marches the German chief of staff Moltke learns (from the Parisian newspapers) that the French forces are marching on Metz, and immediately orders the two Prussian armies to block the French advance.
1st September 1870: battle of Sedan.
4th September 1870: proclamation of the Republic in Paris.
10th May 1871, Treaty of Frankfurt: Annexation of Alsace and Lorraine