German unification was more or less complete after the Seven Weeks' War; while it is true that victory over France in 1871 convinced those remaining principalities to cede to Prussia, I don't think it was the only thing that could have done so. Even without the thorough embarassment set upon the French by that war - or the desire for revenge after losing Alsace and Lorraine, a unified Germany would have been the beginning of many problems for Europe. [...] That Germany was able to combine these would have most likely still kicked off the arms race in the 1890s-1900s, though perhaps with less Franco-Prussian animosity.