Hardly a nation, it is a small independent principality just beyond the Italian border at the western limit of the Gulf of Genoa, practically facing La Spezia.

It was originally a Genoese fortress, in the charge of the Genoese Grimaldi family. It had a population of under 20,000 in 1943. Today the population is just over 32,000. But you are right in that an invasion there would land you in France, not Italy. It was linked up to France in the 19th century.