In 1865 a scheme of a different sort, and of momentous consequences, grew into shape. It was a scheme of which Cavour first guessed the possibility, as well as the far-reaching results. In August 1865 Count Bismarck asked General La Marmora whether Italy would join Prussia in the contingency of a war with Austria? Only a year before he was still thinking of carrying out his policy with the aid of Austria, and he had offered to help her to wrench Lombardy from Italy (and from France if she intervened), in payment for her consent to his designs. But now, though the Austrians did not even remotely suspect it, his thoughts were resolutely turned to the Italian alliance. Without this alliance Italy might, indeed, have acquired Venice, but would the German Empire have been founded?
For a time the proposal was suspended, owing to the temporary understanding concluded between Prussia and Austria at Gastein; and in the interim, General La Marmora urged the Viennese Government to cede Venetia in return for a compensation of five hundred million francs. But those whom the gods would destroy they make mad. Austria preserved her infatuated sense of security almost till the rude awakening caused by the rifle-shots that ushered in the campaign of Sadowa.
One thing which contributed to keeping Europe in the dark as to the impending cataclysm was the character and known tendencies of King William I. of Prussia, whose conservative, not to say retrograde sentiments made it difficult to picture him at the head of what was really a great revolutionary movement, in spite of the militarism that surrounded it. With consummate art, Count Bismarck little by little concentrated all his master's ideas about royal divinity in general into one overwhelming belief in his own divine right to be German Emperor, and so transformed an obstacle into the corner-stone of the edifice he wished to build. But this could hardly be foreseen. At the New Year's Day reception of 1866, Napoleon announced an era of universal peace; henceforth all nations were to arrange their differences amicably, as had been done at Gastein If the illusion was complete, it was destined to be of short duration.
In the spring the Prussian proposal to Italy was formally renewed, and this time it was accepted. The secret treaty of an offensive and defensive alliance for three months was signed on the 8th of April. Less than three weeks later, Austria, which was slowly beginning to feel some uneasiness, proposed to Napoleon the cession of Venetia, while exacting from Italy only a simple promise of neutrality in case of war. General La Marmora held the honour of the country and his own to compel fidelity to the prior arrangement with Prussia, and he refused the tempting offer. His choice has been variously characterised as one of common honesty and of uncommon magnanimity; at all events, it was of incalculable advantage to Prussia, which already gave signs of not being a particularly delicate-minded ally. When La Marmora asked Bismarck whether, in case Austria took the initiative of attacking Italy, Prussia would intervene, the answer was 'No.'