Well, there is always the fact that due to some oversight (ICR where I read this once), San Marino and Sweden have technically been at war since the 30YW until 1996 (according to some Italian historian, Marco Guidi, the San Marinese (or whatever the adjective is) representative at the peace of Westphalia went home without signing anything since he didn't get his salary. This sounds suspicious though, I can't find any reference to where he claimed that, and San Marino was AFAIK not even involved in the war in the first place.). But I agree with Yanez, San Marino has outlasted any other republic in Italy - Venice, Genova (the two biggies), Florence, Siena and Pisa, Lucca etc - solely because it is too small to matter. Again, can't remember the source, but IIRC the army is only 300 soldiers. And if San Marino were to join with the Romagna (then it would be a Romandiola/Marcher state) or lead Italian unification (then the name of San Marino would only be the official name of the Repubblica most likely, while the shorthand would be Italy), so it would sort of lose itself to the greater whole.