reduit

thumb|A reduit in the German fortress of Mainz A reduit is a fortified structure such as a citadel or a keep into which the defending troops can retreat when the outer defences are breached. The term is also used to describe an area of a country that, through a ring of heavy fortifications or through enhancing through fortification the defences offered by natural features such as mountains, will be defended even when the rest of the country is occupied by a hostile power.

==National Reduit== thumb|right|The Antwerp forts, Belgium's National Reduit