In the spring of 1866, the so-called German Confederation, then a loose organisation of autonomous states, was thrown into crisis by a rift between the two largest members, the Austrian Empire, and The Kingdom of Prussia. Since the founding of the Confederation, in 1815, it had been tacitly accepted that Austria was the overseeing authority. Now, however, a more belligerent Prussia sought a leading role. Under a new and ambitious Chancellor, the ruthless Prince Ottovon Bismarck, Prussia would no longer accept a secondary role.
This vital question of leadership naturally affected all member states, and none could ignore it. Matters had, however, moved beyond discussion, and, in June, hostilities began, with the Prussian invasion of the Kingdom of Hanover, and the Electorate of Hesse-Cassel.