Italy, allied to Prussia, declares war on the Austrian Empire.

With Prussia and Austria moving towards war in central Europe, Italy had sensed the opportunity to "redeem" Italian-speaking areas the Austrians now held, like Venetia and Trentino.  Accordingly, Italy and Prussia signed a military alliance in April 1866 and when war broke out, Italy declared war on Austria.  The war did not progress smoothly for the Italians but with Prussian victories and a favorable treaty in October 1866, Venetia and its capital city of Venice were incorporated into the Italian state and the conflict itself dubbed "The Third War of Italian Independence." (By John Osborne)