Most of the German states side with…

Most of the German states side with Austria against Prussia, even though Austria had declared war.

Those that side with Austria include the Kingdoms of Saxony, Bavaria, Württemberg, and Hanover.

Southern states such as, Baden, Hesse-Kassel (or Hesse-Cassel), Hesse-Darmstadt, and Nassau also joined with Austria.

Some of the northern German states join Prussia, in particular Oldenburg, Mecklenburg-Schwerin, Mecklenburg-Strelitz, and Brunswick.

The Kingdom of Italy participates in the war with Prussia, because Austria holds Venetia and other smaller territories wanted by Italy to complete the process of Italian unification.

In return for Italian aid against Austria, Bismarck agrees not to make a separate peace until Italy has obtained Venetia.

Notably, the other foreign powers abstain from this war.

French Emperor Napoleon III, who expects a Prussian defeat, chooses to remain out of the war to strengthen his negotiating position for territory along the Rhine, while the Russian Empire still bears a grudge against Austria from the Crimean War.

This war, the first between two major continental powers in seven years, will uses many of the same technologies as the American Civil War, including railroads to concentrate troops during mobilization and telegraphs to enhance long distance communication.

The Prussian Army will use von Dreyse's breech-loading needle-gun, which can be rapidly loaded while the soldier is seeking cover on the ground, whereas the Austrian muzzle-loading rifles can only be loaded slowly, and generally from a standing position.