In July 1870, France declared because of several reasons war on Prussia. Somewhere I've heard that Austria nearly joined the conflict but only if Italy also supported France, which they didn't. It ended with some great prussian victories and Austria and Italy staying out of the war.
What would have happened if Italy did support France and Austria joined to revenge the former loss to Prussia?
What should France demand and would the WWI we know have happened ( probably not ).
To spice it even more let's say that France didn't have a population decline ( as they had ).