Without his quick response to the Napoleon III ambassador there would be no Franco-Prussian war.
Without Franco-Prussian war there would be no WWI.
Without WWI there would be no WWII.
Otto von Bismarck - Wikipedia, the free encyclopedia
"A suitable premise for war arose in 1870, when the German Prince Leopold of Hohenzollern-Sigmaringen was offered the Spanish throne, which had been vacant since a revolution in 1868. France blocked the candidacy and demanded assurances that no member of the House of Hohenzollern become King of Spain. To provoke France into declaring war with Prussia, Bismarck published the Ems Dispatch, a carefully edited version of a conversation between King Wilhelm and the French ambassador to Prussia, Count Benedetti.
France mobilized and declared war on 19 July, five days after the dispatch was published in Paris. It was seen as the aggressor and German states, swept up by nationalism and patriotic zeal, rallied to Prussia's side and provided troops. Russia remained aloof and used the opportunity to remilitarise the Black Sea, demilitarised after the Crimean War of the 1850s. Both of Bismarck's sons served as officers in the Prussian cavalry. The Franco-Prussian War (1870) was a great success for Prussia. The German army, under nominal command of the King but controlled by Chief of Staff Helmuth von Moltke the Elder, won victory after victory. The major battles were all fought in one month (7 August till 1 September), and both the two French armies were captured at Sedan (Napoleon III was taken prisoner along with the former and kept in Germany for a while in case Bismarck had need of him to head a puppet regime; he later died in England in 1873) and Metz, the latter after a siege of some weeks. The remainder of the war featured a siege of Paris, the city was ”ineffectually bombarded”; the new French republican regime then tried, without success, to relieve Paris with various hastily assembled armies and increasingly bitter partisan warfare.
Bismarck acted immediately to secure the unification of Germany. He negotiated with representatives of the southern German states, offering special concessions if they agreed to unification. The negotiations succeeded; while the war was in its final phase King Wilhelm of Prussia was proclaimed 'German Emperor' on 18 January 1871 in the Hall of Mirrors in the ChÃ¢teau de Versailles. The new German Empire was a federation: each of its 25 constituent states (kingdoms, grand duchies, duchies, principalities, and free cities) retained some autonomy. The King of Prussia, as German Emperor, was not sovereign over the entirety of Germany; he was only primus inter pares, or first among equals. But he held the presidency of the Bundesrat, which met to discuss policy presented from the Chancellor (whom the president appointed).
At the end, France had to surrender Alsace and part of Lorraine, because Moltke and his generals insisted that it was needed as a defensive barrier. Bismarck opposed the annexation because he did not wish to make a permanent enemy of France. France was also required to pay an indemnity."