Franco-Prussian War
Albrecht von Roon, the Prussian Minister of War from 1859 to 1873, put into effect a series of reforms of the Prussian military system in the 1860s. Among these were two major reforms that substantially increased the military power of Germany. The first was a reorganization of the army that integrated the regular army and the Landwehr reserves. The second was the provision for the conscription of every male Prussian of military age in the event of mobilization. Thus, despite the population of France being greater than the population of all of the German states that participated in the war, the Germans mobilized more soldiers for battle.

Q: What was the time span that von Roon acted as minister?
1859 to 1873