Franco-Prussian War
When the news arrived at Paris of the surrender at Sedan of Napoleon III and 80,000 men, the Second Empire was overthrown by a popular uprising in Paris, which forced the proclamation of a Provisional Government and a Third Republic by general Trochu, Favre and Gambetta at Paris on 4 September, the new government calling itself the Government of National Defence. After the German victory at Sedan, most of the French standing army was either besieged in Metz or prisoner of the Germans, who hoped for an armistice and an end to the war. Bismarck wanted an early peace but had difficulty in finding a legitimate French authority with which to negotiate. The Government of National Defence had no electoral mandate, the Emperor was a captive and the Empress in exile but there had been no abdication de jure and the army was still bound by an oath of allegiance to the defunct imperial regime.

Q: The uprising forced a proclamation of what?
Provisional Government and a Third Republic