Which sea did the ancient Romans call Mare Nostrum?

The Mediterranean - our sea - and Rome was the only power ever to hold every shore of it. That is the fact underneath the phrase: it was not a boast about naval dominance but a literal description of a lake inside an empire.

It made Rome possible. Moving grain from Egypt to Rome by sea cost a fraction of moving it a short distance overland - by one Roman price edict, shipping grain across the whole Mediterranean cost less than carting it 120 kilometres - so a city of a million people could be fed from another continent. Every Roman province of consequence touched that water.

Mussolini revived the phrase in the 1920s and 30s as a claim to a new empire, which is why it carries a fascist echo in Italian. In 2013 Italy then used it again, without irony, as the name of a naval operation rescuing migrants from the same water - Mare Nostrum saved something over 150,000 people in a year before being wound down. The same two words have meant imperial possession and humanitarian rescue within a century.