Imperial fortress

Lord Salisbury described Malta, Gibraltar, Bermuda, and Halifax as Imperial fortresses at the 1887 Colonial Conference, though by that point they had been so designated for decades. Later historians have also given the title "imperial fortress" to St. Helena and Mauritius.

The fortresses provided safe harbours; coal stores; and dockyards to protect and supply Royal Navy warships. They had numbers of soldiers sufficient not only for local defence, but also to provide expeditionary forces to work with the Royal Navy, as well as stockpiles of military supplies.