Unification of Germany
Choosing sides

The debate over the proposed national constitution became moot when news of Italian troop movements in Tyrol and near the Venetian border reached Vienna in April 1866. The Austrian government ordered partial mobilization in the southern regions; the Italians responded by ordering full mobilization. Despite calls for rational thought and action, Italy, Prussia, and Austria continued to rush toward armed conflict. On 1 May, Wilhelm gave von Moltke command over the Prussian armed forces, and the next day he began full-scale mobilization.

In the Diet, the group of middle-sized states, known as Mittelstaaten (Bavaria, Württemberg, the grand duchies of Baden and Hesse, and the duchies of Saxony–Weimar, Saxony–Meiningen, Saxony–Coburg, and Nassau), supported complete demobilization within the Confederation. These individual governments rejected the potent combination of enticing promises and subtle (or outright) threats Bismarck used to try to gain their support against the Habsburgs. The Prussian war cabinet understood that its only supporters among the German states against the Habsburgs were two small principalities bordering on Brandenburg that had little military strength or political clout: the Grand Duchies of Mecklenburg-Schwerin and Mecklenburg-Strelitz. They also understood that Prussia's only ally abroad was Italy.

Opposition to Prussia's strong-armed tactics surfaced in other social and political groups. Throughout the German states, city councils, liberal parliamentary members who favored a unified state, and chambers of commerce—which would see great benefits from unification—opposed any war between Prussia and Austria. They believed any such conflict would only serve the interests of royal dynasties. Their own interests, which they understood as "civil" or "bourgeois", seemed irrelevant. Public opinion also opposed Prussian domination. Catholic populations along the Rhine —especially in such cosmopolitan regions as Cologne and in the heavily populated Ruhr Valley—continued to support Austria. By late spring, most important states opposed Berlin's effort to reorganize the German states by force. The Prussian cabinet saw German unity as an issue of power and a question of who had the strength and will to wield that power. Meanwhile, the liberals in the Frankfurt assembly saw German unity as a process of negotiation that would lead to the distribution of power among the many parties.
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