The royal dynasty also built several fortresses and palaces. It had two strong fortresses, in which Seleucus had left his garrisons. Gusuku is the term used for the distinctive Okinawan form of castles or fortresses. Gusuku is the term used for the distinctive Ryukyuan form of castles or fortresses. Prague Castle became one of the largest inhabited fortresses in Europe. These small fortresses reinforced the line of infantry bunkers. Turkish authorities destroyed most of the medieval Bulgarian fortresses to prevent rebellions. Muslim forces retreated in their fortresses and towns. Muslim forces retreated to their fortresses and towns. The Spanish entered Naples and laid siege to the Austrian-held fortresses. Flying Fortresses and 1,156 A-26 Invaders. Full-time Maginot Line troops were accommodated in barracks built close by the fortresses. The defensive lines consisted of a circuit of fortresses and cities. The population dispersed into the mountain top fortresses of the rival kings. Byzantine emperor Theophilus launched an attack against Abbasid fortresses.