I wonder if San Marino has ever been involved in a war. I can't help but think of Bill Bryson's famous adage of how, when Liechtenstein went to war, they left with 80 men and came back with 81 because they'd made a friend along the way.
It was occupied by Germany during WWII after Italy surrendered and they invaded the northern party of it. Only a few weeks until the Allies chased them out though.
I wonder if you need a work visa to work in Italy if you live there, or vice-versa. Also how easy it is to get Italian citizenship. It'd be pretty lousy if you were born there (smaller than Mankato) and then couldn't ever move to Rome or Milan. Do they have to go through customs every time they go to Italy?
The reason it's not part of Italy btw, is during Italy's unification, it was basically the only democratic republic in what is now Italy, and as people who promoted unification were largely arrested and persecuted in their city states and fiefdoms, they usually fled to San Marino. In light of this, the new government of the unified Italian state opted to respect their government's wish not to annex them.