The Franco-Prussian War, in reality a war pitting the French Second Empire against Prussia and its south German allies, completed the process of German unification and fundamentally altered the balance of power in Europe. Its immediate roots lay in the Austro-Prussian War of 1866, whose rapid ending denied French Emperor Napoleon III the territorial and diplomatic concessions he considered the Second Empire's due as Europe's primary power. As he vainly sought compensation from Otto von Bismarck, the Prussian minister-president (prime minister), Bismarck pursued with equal futility a closer political and military relationship with the south German states of Baden, Württemberg, and Bavaria.
Success in the latter endeavor would change European power relationships in ways France could hardly be expected to ignore. Contemporary opinion in fact laid primary responsibility for the events of 1870 at the door of Napoleon III, who allegedly forced a conflict to shore up his unstable regime. Beginning in the 1890s, responsibility was increasingly shifted to a Bismarck described as provoking war in the interests of German hegemony: "blood and iron" in a European setting. Late-twentieth-century scholarship emphasizes Bismarck's desire to keep as many options as possible open for as long as possible. He prided himself on being able to step into a situation and stir things up, confident that he could respond to confusion exponentially better than his associates and opponents. In the spring of 1870 he had his chance.
Bismarck's primary objective was resolving the German question in Prussia's favor. The argument that Bismarck's initial approval of Spain's offer of its vacant crown to Prince Leopold of Hohenzollern-Sigmaringen (a branch of the ruling house of Prussia) was intended to provoke a war overstates Bismarck's belligerence while underrating his self-confidence. The Hohenzollern candidacy was designed to provoke a crisis with France. But it was so managed that at each stage the final initiative, the final choice, remained with Paris. Bismarck recognized that war was an extremely likely outcome of the situation. At the same time he was testing the intentions of the emperor and of France itself.
An international incident is what one of the parties involved wishes to define as an international incident. Negotiating room remained in the first days of July, particularly after Leopold withdrew his candidacy in the face of French hostility. But a French government enjoying its triumph overplayed its hand by demanding that Prussia guarantee the candidacy would not be renewed. Bismarck's negative reply was interpreted in Paris as a justification for a war Bismarck by now also believed inevitable. On 15 July the North German Confederation issued its mobilization orders.
Neither party had a significant advantage in mobilization. The Franco-Prussian War was a classic "come-as-you-are" collision and as such its initial advantages rested with the French. War from a standing start was the kind of conflict
around which France's military system had been developed and refined since Waterloo (1815). The Prussians compensated with speed and system. Helmuth von Moltke, the chief of the general staff, saw the war's true objective as the French army. Decisively defeating it was the best way to convince other powers, Austria in particular, to let half-drawn swords return to the scabbards. And the best way to engage the army was to advance on Paris. The heart of France and of the Second Empire, Paris could not be sacrificed in a strategic withdrawal that in any case was foreign to the French way of war.
Moltke faced two diametrically opposed strategic prospects. The French army might cross the Rhine and hit the Prussians while they were still unloading their troop trains. Or the French might assume the natural defensive positions in which the frontier region abounded, meet the Prussian
advance in a series of encounter battles, then counterattack a weakened, confused enemy. Moltke's response represented a major contribution to the development of what has been called "operational art," the shadowy level between strategy and tactics. He planned to concentrate in the Rhineland/Palatinate area of Prussia, swing his main force south of the French fortress complex at Metz, then advance northwest toward the Moselle and force a major battle before reaching the river.
What the Prussian military strategist Carl von Clausewitz called "fog and friction" affected the Prussians at every turn. Nevertheless, facilitated by a culpably disorganized French mobilization and concentration, the Prussians won a series of initial victories on the frontier and pushed steadily forward. This time it was the French who had a superior infantry rifle, and the chassepot easily stopped German frontal attacks with heavy losses. What decided battle after battle was the ability of the Prussians, and the south Germans who had joined Prussia in the face of what seemed French aggression, to envelop enemy flanks as superior Prussian artillery held the French in place.
By mid-August the main French army had retreated in confusion to Metz. The Prussians got behind it and in a series of battles fought between 16 and 18 August drove the French into the fortress and besieged it. The passivity of French commanders at all levels is indicated by the fact that the Germans were fighting in the wrong direction: facing toward Germany, with their own flanks and rear completely exposed.
Napoleon III, who had escaped encirclement at Metz, organized a relief force from the troops remaining to him. That army was in turn surrounded at Sedan on 1 September and forced to surrender the following day in one of the nineteenth century's most decisive tactical victories. With Napoleon a prisoner, the Second Empire collapsed. The newly created Third Republic of France, determined to continue the war, stamped mass armies out of the ground as another revolutionary government had done in 1793 and set them to relieving Paris, besieged by a Prussian/German army that was unable to develop any other plan for ending the war. These civilian levies proved no match for the Germans in battle. Nor did a burgeoning partisan movement develop any more than a nuisance value. The French maneuvers nevertheless combined to prolong the war to a point at which, despite the favorable terms Germany received, specifically French surrender of the frontier provinces of Alsace and Lorraine, Bismarck and Moltke were desperate to conclude peace and determined to avoid a similar situation in the future.
Once the guns fell silent, Europe rushed to copy the military methods that seemed to have brought Prussia victory. France brooded over its wrongs and losses. A new German empire sought to consolidate its achievements. In less than half a century these consequences would combine in an immeasurably more destructive conflict.
Bucholz, Arden. Moltke and the German Wars, 1864–1871. Basingstoke, U.K., 2001.
Howard, Michael. The Franco-Prussian War: The German Invasion of France, 1870–1871. 2nd ed. London, 2001. Still the standard work, by a master of the craft.
Showalter, Dennis. The Wars of German Unification. London, 2004.
Wawro, Geoffrey. The Franco-Prussian War: The German Conquest of France in 1870–1871. Cambridge, U.K., 2003. Excellent on operational matters.