This policy of Bismarck was proposed by Austria and Prussia at the Diet; the other States refused to adopt it, as they wished to raise the question of succession; on a division Prussia was outvoted. The two great Powers therefore entered into a separate agreement in which, while still recognising the integrity of the Danish Monarchy, they undertook to force the King to withdraw the obnoxious Constitution, and, if he did not consent to do so, they agreed to occupy Schleswig.

The Prussian House, in its address to the King, had declared that the only result of this policy would be to give back the Duchies to Denmark. Was there no fear of this? What would have happened had Denmark after all given in, as England strongly pressed her to do? Had she withdrawn the obnoxious Constitution, and granted all that Bismarck asked, why then Prussia and Austria would have been bound to support the integrity of Denmark, and, if necessary, by force of arms to eject the Federal troops from Holstein. Bismarck had considered this contingency, and guarded himself against it. Many years later Beust put the question to him. "Oh, I was all right," he answered; "I had assured myself that the Danes would not give in. I had led them to think that England would support them, though I knew this was not the case." He had, however, even a surer guarantee than this; the ultimatum presented to Denmark was couched in such a form that even if he would the King could not comply with it. The requirement was that the Constitution should be revoked before the 1st of January. By the Constitution the King could not do this of his own prerogative; he must have the assent of the Rigsrad. This assent could not be obtained for the following reasons: the Rigsrad of the old Constitution had been dissolved and had no longer a legal existence; a new assembly could not be summoned before the 1st of January—there was not time. If an assembly were summoned after that date, it must be of course summoned according to the new Constitution. To do this, however, would be to bring the obnoxious Constitution actually into force, and would mean, so to speak, a declaration of war against Prussia. If the King wished to give in he must have time; he must be allowed to summon the new assembly, lay before it the German demands, and require it to declare its own revocation. The English Government, still anxious to keep the peace, represented to Bismarck the dilemma in which he had placed the Danes. Lord Wodehouse, who was in Berlin in December, requested that at least more time should be allowed. Bismarck refused to listen to the request.

"These constitutional questions," he said, "had nothing to do with him; the Danes had put off the Germans for years; they could not wait any longer. The King could always make a coup d'état; he would have to do so sooner or later. Germany and Denmark could never be at peace so long as the Democratic party had the authority."

Denmark did not give way; the help from England, on which they had reckoned, was not forthcoming; the fatal day passed; the Austrians and Prussians entered Holstein, marched across that Duchy, and in the early part of February began the invasion of Schleswig. The relations of the Allied troops to the Federal army of occupation were very remarkable. Both were opposed to the Danes, but they were equally opposed to one another; had they dared to do so, the Saxons would have opposed the Prussian advance. As it was they sullenly watched the Prussian and Austrian columns marching north to the invasion of Denmark.

It was the first time that the remodelled Prussian army had been tested on the field of battle; Bismarck had brought it about that they were fighting for the cause of Germany and in alliance with Austria. As soon as war began, his own position improved. The King and the army were, of course, all the more confident in a Minister who had given them so good a cause of war and allowed them to take the field side by side with their old ally. Their superiority in number and discipline ensured success in the military operations; the Danes evacuated their first position at the Dannewirk; the German troops occupied the whole of Schleswig, then after some further delay advanced into Jutland, and finally began the siege of the strong fortification of the Düppel. The taking of this was a difficult piece of work, which, after some delay, was successfully carried out at the beginning of April.

Meanwhile the diplomatic difficulties had continued. There had now come from England the proposal of a Conference. This Bismarck, always wishing to preserve the appearance of moderation, accepted. Before doing so, he knew that he had gained a very important ally. Napoleon was displeased with the English Government; he it was who suggested to Bismarck that the best solution of the difficulty would be the annexation of the Duchies to Prussia. It was just what Bismarck himself desired. Would he be able to bring it about? This was what was in his mind when he had to consider the attitude he should adopt at the Conference.

He could not, of course, propose it openly; he might be able to arrange affairs so that in the universal confusion this solution should be welcomed. He first of all began to change his attitude towards the German agitation for Augustenburg; hitherto he had opposed and discouraged it; now he let it have free course. He wrote:

"The present situation is such that it seems to me desirable to let loose the whole pack against the Danes at the Congress; the joint noise will work in the direction of making the subjugation of the Duchies to Denmark appear impossible to foreigners; they will have to consider programmes which the Prussian Government cannot lay before them."

What this means is that England and Russia were to be convinced that Denmark could not regain the Duchies; then they would have to consider who should have them. Bismarck believed that Austria was irrevocably opposed to Augustenburg. "She would rather see the Duchies in our hands than in those of the Prince," he wrote. Austria and Russia would, therefore, oppose this solution; if both Denmark and Augustenburg were impossible, then would be the time for France to ask why should they not be given to Prussia, and to join this proposal with another one for the division of the Duchies according to nationality.

Napoleon, in accordance with his principles, wished entirely to disregard the question of law; he was equally indifferent to the Treaty of London, the hereditary rights of Augustenburg, or the chartered privileges of the Duchies. He wished to consult the inhabitants and allow each village to vote whether it wished to be German or Danish; thus, districts in the north where Danish was spoken would then be incorporated in Denmark; the whole of Holstein and the south of Schleswig would be permanently united to Germany, and by preference to Prussia. These revolutionary principles of Napoleon were in the eyes of the Austrian statesmen criminal, for if applied consistently not only would Austria be deprived of Venetia, but the whole Empire would be dissolved.