The Great German Nationalist War of 1870

From the ghetgo, bismarck was re starting the project of german unification. He believed the best way to make prussia strong was to make it the leader of a unified germany. So he spent the whole rest of the 18 sixties trying to make Prussia the leader of  unified Germany. To explain the eventual franco prussian war that comes in 18 70, where do we need to begin? Where else would we start but the duchies of schleiswig and holstein? This had led to a shooting war starting up in 18 forty that we called the first schleswig holstein war.