The Franco-German War, which started on July 19th, 1870, completed the process of German unification under Prussian Prime Minister Otto von Bismarck (1815–1890), nicknamed the “Iron Chancellor” because of his strong conviction that’s sometimes the use of force was inevitable.
Its roots lay in the German War or Austro-Prussian War of 1866, which had confirmed Prussian leadership of the German states and concluded with the formation of the North German Confederation as well as the end of Austria’s influence in German politics in the strict sense of the word.
Most of all, it threatened France’s status as continental Europe’s primary power, as Prussia sought to incorporate the southern German kingdoms of Bavaria, Württemberg, Baden and Hesse-Darmstadt into the new entity, but Paris was strongly opposed to any further alliances of German states.
Besides that, Bismarck’s initial approval of Spain’s offer of its vacant crown to Prince Leopold of Hohenzollern-Sigmaringen (1835-1905) in June 1870 irritated France. It feared encirclement by Prussia and its expanded influence due to a potential new ally on the Iberian Peninsula.
Leopold quickly withdrew his candidacy in the face of French hostility. However, Prussia declined to guarantee it wouldn’t be renewed, which was seen in Paris as a potential justification for military action.
Furthermore, Bismarck edited an official dispatch Prussian King William I (1797-1888) sent from the health resort of Bad Ems, in which the regent informed him about his refusal to have another meeting with the French Ambassador in Berlin, Vincent Benedetti (1817-1900) about this very sensitive topic.
It was published on July 14th and deeply angered French Emperor Napoleon III (1808– 1873), who overreacted and declared war on Prussia the next day.
Initial advantages definitely rested with the French, as France’s military system had been refined since the lost Battle of Waterloo on June 18th, 1815. France also had great faith in two recent technical innovations: the chassepot rifle and the mitrailleuse, an early machine gun with wheels and significant firepower, but somehow lacking range and mobility. On the other hand, the Prussians possessed superior artillery clout thanks to modern six pounder cannons.
However, although the French mobilized a total of 1.600,000 troops, at the beginning of the hostilities its army could field only 335,000 men. This was due to fast, though at the same time culpably disorganized mobilization and concentration.
In contrast, Prussia soon had about 520,000 men ready out of 1.400,000. Superior organization and mobility enabled the chief of the general staff, them an institution unique in Europe, Field Marshal Helmuth von Moltke (1800-1891), to logistically exploit German superiority in numbers, also by the prompt and systematic usage of railroads.
Various clashes in August basically already sealed the fate of France: from the failed occupation of Saarbrücken from the 2nd to the 4th and the lost Battle of Weissenburg on the same day, to the defeat in the Battles of Spicheren and Wörth on the 6th, continuing with standoffs at the Battles of Mars-La-Tour on the 16th and Gravelotte on the 18th.
Afterwards, part of the French Army retreated in confusion to the fortress of Metz, which would be sieged until General François Achille Bazaine (1811 -1888) capitulated with his 173,000 troops intact on October 27th.
The Battle of Sedan on September 1st proved most decisive, as on the 2nd Napoleon III, who had escaped encirclement at Metz, together with General Patrice de Mac-Mahon (1808-1893), and his entire army of more than 100.000 soldiers were taken all prisoners. German losses only numbered 460 officers and 8,500 men.
The Second French Empire simply collapsed and the monarch was later sent to Wilhelmshöhe Castle near Kassel. It was a chaotic situation, as there had been no abdication and the Army still felt bounded by an oath of allegiance to the defunct imperial regime.
A French new government of national defense with no electoral mandate assumed power on September 4th. It proclaimed the deposition of the captive Emperor, whose Spanish wife Eugénie de Montijo (1826-1920) would soon go into exile in England. The Third Republic decided to continue to fight and tried to relieve Paris, besieged by the Germans since September 19th.
The Prussians pushed steadily forward. French victories at Coulmiers on November 9th, Villepion on December 1st and Villersexel on January 9th, 1871, and holding the fortresses of Bitsch and Belfort couldn’t change the final outcome. After long negotiations that had started in early September 1870, the fourth round of January 28th, 1871 brought a breakthrough and Paris surrendered.
It included a provision for the election of a French National Assembly on February 8th that would have the legal authority to conclude a definite peace. After a ceasefire across France was announced on January 31st, a temporary settlement was signed on February 26th and ratified on March 1st.
The formal Treaty of Frankfurt (called Frieden von Frankfurt, Peace of Frankfurt in German) was inked on May 10th. France recognized the new status of Wilhelm I, who had been proclaimed Kaiser at the Hall of Mirrors in the Palace of Versailles on January 18th, 1871.
The huge indemnity of five billion francs, proportioned according to population, turned out to be the exact equivalent to the one imposed by Napoleon Bonaparte on Prussia by the Treaty of Tilsit on July 9th, 1807. Germany would continue to occupy French soil until the payment was complete.
The Reich reacquired the German-speaking region of Alsace and those of nearby Lorraine, taking also Metz and Château-Salins, to establish the Reichsland Elsaß-Lothringen. The clear German victory fundamentally altered the European balance of power.
Nevertheless, until Bismarck’s dismissal on March 20th, 1890 by William II (1859-1941), stability was still ensured and the new German empire sought to consolidate its achievements, even slowly becoming interested in colonial acquisitions.
On the other hand, as France was determined to recover Alsace-Lorraine at all costs, extremely instability marked the period of peace from 1871 to 1914. A deep sense of bitterness, hatred and demand for revenge gave birth to French Revanchism, one of the causes of World War I (1914-18), after which the French would achieve their main goal.
The legend of Prussian militarism was born and alive until the Allies disbanded this German heartland on February 25th, 1947. Simultaneously, the extremely effective, innovative Prussian command system was soon adopted by other great powers.
The concept of continuous study of all aspects of war, including previous operations to avoid repeating mistakes, and for drawing up and reviewing plans for mobilization or campaign, seemed revolutionary at the time, as was universal conscription.
P.D.: The Kingdom of Italy was also officially unified on September 20th, 1870, as the Papal States were finally absorbed into the new country.