Who was Napoleon III captured by during the Franco-Prussian War?

Napoleon III was captured by Prussian forces during the Franco-Prussian War, which took place from 1870 to 1871. His capture occurred during the Siege of Sedan in September 1870. The defeat of the French army at Sedan was a decisive moment in the war, leading to the collapse of the Second French Empire and the eventual establishment of the French Third Republic. The Prussian army, under the command of General Helmuth von Moltke, was instrumental in the rapid and effective military campaign that led to this significant capture.

The other options involve forces that were not directly engaged in the Franco-Prussian War against Napoleon III at that time. The Italian forces had their own conflicts but were not involved in this particular war. The British army, while an important military force in Europe, did not intervene in the war. The Austrian forces, having had previous conflicts with France, were no longer in an alliance against France by the time of the Franco-Prussian War and did not play a role in Napoleon III's capture. Thus, the correct answer reflects the specific historical context of the conflict and the involved military forces.