North German Confederation
On 18 August 1866, Prussia and most of the north German states signed the August Treaty. They agreed on a military alliance and declared their intention to create a federal state. (Some other states joined soon.) A federal state is different from an alliance as it has a federal government and legislation, and it is different from a unitary state as there are still rather powerful states below the federal level. Plans for a federal state in Germany had existed since the year 1848.