The Treaty of Nice was a military alliance treaty signed by

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

and

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

and revealed on September 5, 1892. The consequence of the treaty was that if one the signatories was attacked in an

act of war A (; ) is an act or an event that either provokes or is used to justify a war. A ''casus belli'' involves direct offenses or threats against the nation declaring the war, whereas a ' involves offenses or threats against its ally—usually one b ...

, the other signatory must

declare ''Declare'' (2000) is a supernatural spy novel by American author Tim Powers. The novel presents a secret history of the Cold War, and earned several major fantasy fiction awards. Plot summary The non-linear plot, shifting back and forth in tim ...

war on the attacker if requested.http://www.eecs.umich.edu/~joshual/Pax/Tertius/treaties.html
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Notes

19th-century military alliances 1892 treaties Treaties of the French Third Republic Treaties of the Kingdom of Italy (1861–1946) Military alliances involving France Military alliances involving Italy 1892 in France 1892 in Italy September 1892 events {{Treaty-stub