This is something I've been wondering about: at the end of the 1866 Austro-Prussian war King Wilhelm I wanted to annex parts of Austria but was persuaded not to by Chancellor Bismarck, who saw that taking territory from the Habsburgs would end any chance of a later alliance. So lets say Wilhelm gets his way and annexes at least some parts of Austria (maybe Austrian Silesia?). What is the short and long-term repercussions of this action? Would this lead to Austrian participation in the Franco-Prussian war? If not, would we see a later Franco-Austrian alliance aimed at retaking their provinces from Germany? Or was a Austro-German alliance inevitable?