At last an event occurred which showed his hand. In November, 1863, Frederick VII., the king of Denmark, died. By his death the Schleswig-Holstein question again burst upon distracted Europe,—Who was to reign over the two Danish provinces? The king of Denmark, as Duke of Schleswig and Holstein, had been represented in the Germanic Diet. By the treaty of London, in 1852, he had undertaken not to incorporate the duchies with the rest of his monarchy, allowing them to retain their traditional autonomy. In 1863, shortly before his death, Frederick VII. by a decree dissolved this autonomy, and virtually incorporated Schleswig, which was only partly German, with the Danish monarchy, leaving the wholly German Holstein as before. Bismarck protested against this violation of treaty obligations. The Danish parliament nevertheless passed a law which incorporated the province with Denmark; and Christian IX., the new monarch, confirmed the law.
But a new claimant to the duchies now appeared in the person of Frederick of Augustenburg, a German prince; and the Prussian Chamber advocated his claims, as did the Diet itself; but the throne held its opinion in reserve. Bismarck contrived (by what diplomatic tricks and promises it is difficult to say) to induce Austria to join with Prussia in seizing the provinces in question and in dividing the spoil between them. As these two Powers controlled the Diet at Frankfort, it was easy to carry out the programme. An Austro-Prussian army accordingly invaded Schleswig-Holstein, and to the scandal of all Europe drove the Danish defenders to the wall. It was regarded in the same light as the seizure of Silesia by Frederic the Great,—a high-handed and unscrupulous violation of justice and right. England was particularly indignant, and uttered loud protests. So did the lesser States of Germany, jealous of the aggrandizement of Prussia. Even the Prussian Chamber refused to grant the money for such an enterprise.