Gastein therefore marks a setback in the development of Bismarckian politics: the war is premature, it is necessary to prepare for victory with tranquility. In the meantime, the conference in Biarritz is from the following November, where Napoleon gives assurances of peace, but without specific commitments, and makes it clear that in any case it is necessary to agree with Italy, and the Italo-Prussian trade treaty – what he wants first of all, the recognition of the young Italian state by the Bund. In January 1866, a lively exchange of notes between Prussia and Austria darkens the horizon and suggests that the storm is imminent. In the spring, General H. von Moltke, who had expressed his conviction on the need for an Italo-Prussian alliance, went to Italy to negotiate at the same time as the departure for Berlin of General Germany Govone. The negotiations take place in an atmosphere of scarce confidence, and therefore of perplexity on the part of Italy, which, after the recent experience, has not failed in the meantime to test the ground in Vienna in order to obtain Venice peacefully; until a treaty of alliance is drawn up (April 8), valid for three months, which has the double advantage for Prussia of ensuring her Italian military aid and at least the non-hostility of Napoleon, who poses as the protector of Italy. On a secret note, Austria not only expresses its intention to defer to the Bundestag the solution of the Schleswig-Holstein question, but it certainly speaks of the mobilization of the Confederate army against Prussia. Bismarck has immediate knowledge of the note, and asks the German governments what their behavior would be in the event of an attack by Austria and at the same time announces the urgent need for a reform of the Bund. Proposals for an immediate Bundestag meeting followto discuss the reform of the constitution. All this finds little resonance, due to the sudden violent resurgence of particularisms and confessionalisms, and has dangerous repercussions also on the position of Bismarck, attacked by various parties which demand his removal. The not entirely clear demeanor of France and the general lack of confidence in a Prussian victory, on the other hand, increase the perplexity of the king, influenced by the queen and the heir to the throne. Bismarck comes out unscathed from a first attack. Meanwhile, Napoleon III proposes the convening of a congress, to settle both the question of the duchies and that of Venice, but Austria declines the proposal, preferring to agree with France. The violation of the Gastein treaty by the Bund to mobilize the federal army against Prussia. The request is accepted by a majority; the Prussian representative leaves the assembly and Prussia announces the dissolution of the Bund to the European powers. It now follows its own path. On June 16, even the king, now sure of Russian neutrality, is persuaded of the inevitability of war.
The lightning-fast victories of the Prussian armies (see Austro – Prussian, war) cause general astonishment. France had tried to avoid war and had also prepared a program to define the Austro-Prussian conflict; for its part, Austria had promised Napoleon to cede Venice to him, as long as he intervened as a mediator between Austria and Italy. The evident purpose of the offer was to break the Italian-Prussian alliance and to be able to fight on one front only. Now here is that two days after the Prussian victory of Sadowa, considered by France, very alarmed, as its own defeat, that is to say at the same moment in which, the dissidents in the Italian command that had led to Custoza, the army, almost double the opponent, was preparing to cross the Po to seek revenge, Napoleon had it published in the Moniteur that Austria ceded Venice to the Emperor of France and asked him to intervene as mediator with Prussia and Italy. Prussia is surprised and indignant at this unsolicited mediation, while Italy rises with a unanimous cry of protest, unwilling to lay down its arms or receive Venice from France. But Napoleon insists and implies that Prussia must be content with Northern Germany, then proposes the Main line as the southernmost border of Prussian political influence. Bismarck, fearing further and dangerous French interference, is now in urgent need of concluding the peace and managing to win, this time with the support of the crown prince, the opposition of the king, who, at first reluctant to accept war, now wants large rewards., asks and gets the annexation of Hanover, of electoral Hesse, of the cities of Nassau and Frankfurt. We are thus, quickly, at the Nikolsburg peace preliminaries, which ended before the approval of Italy, which was assured of the sale of Venice, but not that of Trentino that the whole country was demanding. The peace, which was concluded in Prague on 23 August, is still complicated by the Russian claims and by the request, by France, of compensation such as to be excessive for Ambassador V. Benedetti himself; but Bismarck replies that if the rejection of such claims must mean war, Prussia assumes all the responsibility. Napoleon does not insist, and Bismarck takes advantage of French requests to develop his plan. He managed, in fact, to obtain the written document of the claims of France, very harmful to the interests of the southern states – vice versa, shrewdly, he will renounce the annexation of some Bavarian territories located north of the Main – and uses them to gain the sympathy and trust of them and conclude, on the eve of the peace of Prague, treaties of defensive and offensive alliance with Württemberg, Baden and Bavaria. Thus, with the war of 1866, Bismarck annexed some small states of the north and the duchies of Elba, eliminated the direct influence of Austria in the German states, without however humiliating the pride of the enemy, already thinking of an Austrian alliance. Prussian, finally linked the southern states to Prussia with military alliance treaties, which means that in the event of war all of Germany is united under the military leadership of Prussia.
But Bismarck does not rest on Sadowa’s laurels. The military victory has undoubtedly made the internal struggle in front of the parties enormously less bitter, which now even they cannot escape the need to adapt to the new situation. Thus the progressive party, tenacious opponent of the army reform, suffered in the new elections, held in the warm atmosphere of the Prussian victories, a resounding defeat, to the advantage of the old liberals and conservatives, and, immediately after, a fracture, with the detachment of a notable group of its representatives who form the national party (Nationalliberale Partei) and place themselves at the disposal of the government. The conservatives also split, and some of them form the party of the liberal conservatives (Freikonservative Partei). So that Bismarck’s policy now has solid foundations also in Parliament and can continue its development, despite some difficulties that come from the resistance of the annexed states.
With the peace of Prague, Austria had to accept the dissolution of the German Bund and recognize the Norddeutscher Bund, formed by Prussia, which includes twenty-two states (see Northern Germany, Confederation of the). It is not yet the time, despite the patriotic and disinterested insistence of the Grand Duke of Baden, to think of gathering the southern states around Prussia, where many still look to Austria with nostalgia and hope; but if political unity is premature, the solution of the economic problem seems urgent to all, and Bismarck, at the end of 1867, presents the project for a new Zollverein which, after not a few prevarications and resistance, is accepted by all the German states. The relative treaty is valid for eight years, at the end of which it is intended to be renewed for another twelve, if no denunciation has been made. Thus, around Prussia, Bismarck tightens even more the ring of his unitary program. Now only political welding is missing.