the fluvial flotillas (classes) under the command of the riverine duces. The Notitia gives no information about the Rhine flotillas (as the Rhine frontier had collapsed by the time the Western section was compiled), but mentions 4 classes Histricae (Danube flotillas) and 8 other classes in tributaries of the Danube. Each flotilla was commanded by a praefectus classis who reported to the local dux. It appears that each dux on the Danube disposed of at least one flotilla (one, the dux Pannoniae, controlled three). Weapons manufacture In the 4th century, the production of weapons and equipment was highly centralised (and presumably standardised) in a number of major state-run arms factories, or fabricae, documented in the Notitia. It is unknown when these were first established, but they certainly existed by the time of Diocletian. In the 2nd century, there is evidence of fabricae inside legionary bases and even in the much smaller auxiliary forts, staffed by the soldiers themselves. But there is no evidence, literary or archaeological, of fabricae outside military bases and staffed by civilians during the Principate (although their existence cannot be excluded, as no archaeological evidence has been found for the late fabricae either). Late fabricae were located in border provinces and dioceses. Some were general manufacturers producing both armour and weapons (fabrica scutaria et armorum) or just one of the two. Others were specialised in one or more of the following: fabrica spatharia (sword manufacture), lanciaria (spears), arcuaria (bows), sagittaria (arrows), loricaria (body armour), clibanaria (cataphract armour), and ballistaria (catapults). Fortifications Compared to the 1st and 2nd centuries, the 3rd and 4th centuries saw much greater fortification activity, with many new forts built. Later Roman fortifications, both new and upgraded old ones, contained much stronger defensive features than their earlier counterparts. In addition, the late 3rd/4th centuries saw the fortification of many towns and cities including the City of Rome itself and its eastern sister, Constantinople. According to Luttwak, Roman forts of the 1st/2nd centuries, whether castra legionaria (inaccurately translated as legionary "fortresses") or auxiliary forts, were clearly residential bases that were not designed to withstand assault. The typical rectangular "playing-card" shape, the long, thin and low walls and shallow ditch and the unfortified gates were not defensible features and their purpose was delimitation and keeping out individual intruders. This view is too extreme, as all the evidence suggests that such forts, even the more rudimentary earlier