Prussia emerged from the Napoleonic Wars as the second most important of the German states.
At the Congress of Vienna in 1815, Prussia gained important territories including the Rhineland:
Prussia's development as a successful, modern industrial state gave hope to German nationalists.
Economically, unification through the Zollverein economic alliance of 1834 had been a success.
Attempts at a political union, mainly on the Prussian side, had failed. The Austrians were too strong both politically and militarily.