Recently I've been reading about the Treaty of Turin (1860) between Italy and France. In this treaty, Savoy and Nice were annexed into France from the Kingdom of Sardinia. I have several questions about the treaty and its effects today:
a) Why only Savoy and Nice?
b) Were these regions mostly french-speaking/french-populated?
c) Borders don't always reflect the ethnicities of people living in the area, so in 1860 which areas were predominately Italian and which areas were predominately French?
d) How much were these regions changed by 1996?
e) What is the true cultural border between France and Italy? When I look at a modern ethnic map of Europe, it always strikes me that everything west of the northern Italian border is 100% French, as if the extent of the French-inhabited areas stop there; vice versa for Italian-speaking areas.
Why only Savoy and Nice?
The main reason for that was Napoleon III's initial desire to draw a new border based on the 'nationality' (as it was understood in the 19th century) of its inhabitants; Cavour was willing to cede Savoy but Nice was another matter altogether as the county in question was, he retorted, more Italian than French. This didn't deter Napoleon from pushing his demands, though: demands which Cavour was almost forced to agree in the face of an increasingly unfavourable international situation in 1858 - but not without resistance from both his Cabinet and the Court.
Were these regions mostly french-speaking/french-populated?
Actually... no. Or at the very least, not quite.
Only Savoy and the Val d'Aosta could've been considered culturally closer to France than they were to the rest of the Peninsula; whereas the former county (then division) of Nice was for the most part populated by Ligurian speakers.
And I'm saying say 'closer' because those inhabitants were hardly French in the modern sense of the word; they would become such, and were made to learn that language, only after 1860. Instead these people belonged to different cultures and spoke either Franco-Provençal dialects - like Valdôtain - or languages (Occitan, Savoyard).
[...] in 1860 which areas were predominately Italian and which areas were predominately French?
Again... only the divisions (provinces) of Annécy and Chambéry - that'd be Savoy as a whole - as well as the Val d'Aosta, which at the time was included within the division of Turin, could somehow be considered as such.
How much were these regions changed by 1996?
I'd say - quite obviously - much. Not least because after the annexations of 1860 the Italian population of Nice was forcibly expelled and/or frenchified; then in 1947 a few areas of Piedmont (Briga Marittima, Tenda) and Liguria (the Roia valley) were ceded as war reparations to France, which actively sought to annex the Val d'Aosta and Ventimiglia as well.
What is the true cultural border between France and Italy?
Well, I'm afraid that you're looking at it!
Apart from the areas annexed in 1947 - whose current cultural status is in all fairness unknown to me - I guess that 150 years of French rule, followed by the mass exodus of the local inhabitants and the following waves of immigrants from both the rest of France and abroad, have inevitably split the cultural border among the lines of the political one.