The Claudian invasion of 43 A.D. see Roman Invasions website and the following years of conquest saw the ingress of an almost alien culture into the region that comprises the county of Yorkshire.  That is not to say that the Romanic culture was unheard of, trade had seen to that.  The people of the largely water accessible lands, which are now Yorkshire, were in constant trade both with their southern neighbours, and cultures on mainland Europe.  Roman trade goods found their way into the local Iron-age societies of the Garbrantovces who occupied the southern coastal fringes of the county; the Parisi who occupied much of what is now the East Riding; and the Brigantes, a confederation of smaller tribes, who occupied the bulk of the remainder of the county and beyond.   The Roman military occupation of Yorkshire did not commence until the year 71 A.D., subsequent to the quelling of the valiant but in vain defence (often called revolts, which has always mystified me, as they were defending their own homelands and culture) put up by southern British peoples such as the Iceni of East Anglia and the Silures of southern Wales.  The Legio IX Hispana, commanded by Petilius Cerlialis, who was also governor of the newly to be acquired territory, had used the natural barrier of the Humber Estuary, then more torpid and broad than now, as their front line with a northern extension of Ermine Street from Lincoln (Lindum) to the estuary's southern shore at Winteringham.  The thrust across the Humber into the lands of the Parisi and the Brigantes at that point was obviously foreseen, though the means of crossing have not been determined.  There are three possibilities.  One; there was a passable ford at that point (a known fording place from pre-history is known to have existed a short distance eastwards at North Ferriby, which was not then utilised); two, the legion was transported across by boats (the favoured option as there is evidence of it being a ferry point); and three, there was a temporary bridging structure.  The latter option has not I suspect been seriously investigated, but I feel that such a structure was not beyond the capabilities of legionary engineers.  The drawback, as I see it, to the use of boats is a simple military one; if serious opposition was encountered then any means of withdrawal was dependant upon such boats still being available. 

There are no surviving contemporary texts describing the advance of Petilius Cerlialis, just as there remains no knowledge of any resistance that might have occurred.  However, the fact that there were built three or four (the total number is in doubt) forts along the western scarp of the Wolds in a distance of 33 miles, (those at Filey and Stamford Bridge are uncertain) would indicate some sense of insecurity as they followed the line of demarcation between the Parisi and the Brigantes.  It has been suggested that the Parisi were already highly Romanised, and that they allowed passage of the IXth Legion.  The move over the Humber was however part of a grander strategy to conquer the Brigantes, who were more resistant to the Empire.  The thrust north and westwards, with large forts at York (Eboracum) and Malton (Derventio), enabled a pincer movement to develop, with the Legio XX commanded by Gnaeus Julius Agricola advancing further west.  Agricola marched his men north along what is today the road called the A1 (The Great North Road) through Doncaster (Danum), Castleford (Legiolium), Newton Kyme, Aldborough, and Catterick (Cataractonium), after which, at what is today Scotch Corner, the road divided with one branch leading towards Greta Bridge, and the other towards Piercebridge.  It was at Aldborough where Ermine Street joined with the road from the southwest.  Another road linking up at Aldborough was a cross-country route from Ribchester (Bremetennacum) in Lancashire via Ilkley (Olicana), and York (Eboracum).  Another crossed the Pennines from Manchester (Mancunium) again to York.  The vast majority of Roman fortifications within the county are Flavian, that is to say, they date from the period 69 A.D. to 96 A.D., which encompass the imperial reigns of Vespasian, Titus, and Domitian.  The obvious conclusion drawn from this is that after the initial conquest, most of the native populations had acquiesced to their new condition, and posed no or little threat to the newly imposed Roman status quo.  This was an assumption, in the case of the Brigantes, which was to prove erroneous.  Prompted by the depletion of Yorkshire garrisons required for the construction of the Antonine Wall, the Brigantese revolted in the year 155, even threatening the southern side of Hadrian's Wall.  They were effectively and efficiently repressed by C. Julius Verus.  A second period of unrest occurred in the year 300, when the Brigantes once again showed that they were not fully defeated in spirit.  It was a time of virtual civil war in Britain, which was eventually quelled by Constantius Chlorus.   

When the Romans did arrive, they arrived in force with the intention of staying.  The proliferation of forts in the 1^st century A.D. is evidence.  Other military sites of occupation include Roman roads, which do not seem on the face of it, very military.  However, the reason for their construction was purely military, and it was the legionary soldiers and engineers who built them.  They ought therefore be included here as military sites or features, but due to the uncertainty of many of their routes, it is not possible to incorporate them here.  It is also unfortunate that the current archaeological record of the network of roads in the county is incomplete, but conversely, it does provide scope for some interesting speculation where known roads simply stop in the middle of apparent nowhere.  The other military sites, which should be included, are the coastal signal stations.  The known ones are where they would be expected, on high prominent headlands where possible, but essentially in line of site with adjacent stations.  Once again there are gaps in the archaeological record, once again, educated speculation can point to others that might have been lost due to coastal erosion.  The signal stations were built to warn of incursions from mainland Europe, where the nations of Angles, Saxons, and Jutes, were beginning their westward migrations.  The stations were intended to warn of such landings, so that local militia, and legionary support could be called to the location without delay.  They date from the very last phase of occupation, the late 4^th century, thereby making them the final element of Roman suppression.  It has been theorised, with some military justification I think, that there was also a line of similar signal stations running south from Flamborough Head to Spurn Point at the mouth of the Humber Estuary.   However due to the ongoing and much publicised coastal erosion of the Holderness coast, any such sites will have long vanished beneath the cold waters of the North Sea, along with about 30 sites of habitation.  Indeed, homes and houses are still being washed away.  The military need for such stations is obvious when the coast line is viewed, it is quite low lying, with clay cliffs seldom more than 30 feet high, an easy target for raiding parties of Germanic freebooters.  Because of the relatively flat nature of the coast, it has been suggested that no more than 4 signal stations would have been required.  It might seem that undue attention is here being paid to sites which no longer exist, but that is the point, they cannot be included in the body of the list of military sites, so their existence, or likely existence must perforce be mentioned here.    

The legions were withdrawn from the British Isles by the emperor Honorius in the year 410 or there about, after which began a series of invasions, settlements, call them by what ever name, until the final and truly devastating invasion, that of the Normans, which led to the virtual destruction of the entire county, and its population, know to history as the Harrying of the North a thousand years after the arrival of Petilius Cerlialis and his IXth Legion, but that is another story.  

In conclusion, while this list is as inclusive as history and archaeology currently allow, it cannot be said to be a complete record of Roman military sites in the county, previously unknown sites keep appearing from time to time that will, hopefully, see a continuing interest in the subject from both historical researchers and archaeologists.