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 Dueppel.

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.