The Affaire of Neuchâtel gathers the coup d'etat monarchist of 1856 and the crisis between the Suisse and the Prussia which followed.

The county of Neuchâtel and the principality of Valangin had chosen the King de Prusse as sovereign when the local dynasty was extinct. This choice had been dictated by the distance of the sovereign who was to thus guarantee a broad local autonomy.

In 1815, to the Treated of Vienna, the Canton of Neuchâtel is attached to the Swiss Confédération while reaffirming the suzerainty of king de Prusse on the area. At the time of the revolutions of 1848, Neuchâtelois proclaim the Republic without the king of Prussia not reacting. Nevertheless a party monarchist remains in the canton and a group of insurgent seizes the castle of Neuchâtel during the night of the 2 to the September 3rd 1856, imprisoning four advisers of State. La Chaux-de-Fonds and the top of the canton does not recognize the coup d'etat and a counter-attack of the republicans, carried out by Ami Girard, take again the castle and stop more than 500 monarchists.

Vis-a-vis these events, the king of Prussia reacts and threatens to invade Switzerland to defend his rights. The Federal council decides the lifting of a national loan of 6 million Swiss francs to organize defense. The reaction exceeds its hopes, in a few days they are 100 million Swiss francs which are gathered. The general Henri Dufour, who had carried out successfully the federal troops at the time of the Guerre of Sonderbund in 1848 is again with the head of the federal army and is charged to occupy the border of the the Rhine.

Not very eager to see the Prussian troops crossing the river, the European powers, carried out by Napoleon III proposes a mediation successfully. March 5th with the May 26th 1857, a European congress joining together with Paris the plenipotentiary ones of the Austria, the France and the the United Kingdom, obtains from the king Frederic-Guillaume IV of Prussia his full and whole renunciation of its old rights of prince de Neuchâtel. The May 26th 1857, a treaty is concluded in Paris under the terms from negotiations led from the Swiss side by the minister Jean-Conrad Kern who successfully defends the interests and the honor of Switzerland. The treaty lays out that the insurrectionists are amnestied, that the expenses are dealt with by the Federal state and that the king of Prussia gives up his claims on the canton of Neuchâtel. The June 19th 1857, the king of Prussia solemnly unties Neuchâtelois of their oath of fidelity.

External bonds

• the treaty of May 26th, 1857