I want to break these down into three diffrent parts, part 1 will be just a brief introduction as to how the fort(s) came to be, part 2 will be the actual fort of burgh castle in more detail, and part 3 will be the fort in post Roman britain. As with anything when ancient Rome is concerned researching this brings up scandals and plots worthy of epics like HBO's Game of thrones and, well, Rome!
First I should explain why this fort and the rest of the Saxon shore forts were built, it’s hard to know where to start, I could go right back to the Roman occupation of Britain in a detailed way, but this would open up a can of worms that could end up anywhere in the Roman empire, and I would rather stay in Norfolk for this one! Roman occupation of Britain started in 43AD, obviously this was not a smooth transition and various rebellions/resistances arose, most notably the Boudican revolt of 61AD. Despite unrest in the northern areas of Britain the rest of the country remained fairly stable, until the middle of the 3RD century when Angles, Saxons and Jutes began raids along the eastern coast of Britain, only encouraged by the pressures the roman armies were already under in the north. Around the same time the usurper Postumus declared himself Emperor of the new Gallic empire, incorporating Britain, Gaul and Spain. The Gallic empire eventually fell and a new usurper arose in the late 3rd century, Carausius ( a military commander who was charged with the task of dealing with saxon and frankish pirates, but was accused of keeping any treasure for himself, he may even have had dealings with these pirates), he seized control of northern Gaul and Britain, this is where theories of the construction for the forts differ, some say they were constructed as a means of defending the coast against the sea raiders while others say it was created as a way of keeping Britain and northern Gaul (the northern coast of Gaul also had shore forts) secure from the rest of the Roman empire. Both theories are very plausible but I think it is a combination of the two, I think construction of the forts began as a way to protect the coast and trade from pirates, but when the usurpers time arose I believe that they also saw the forts as a way of protecting their frontiers. Anyone defying Rome would be very stupid not to take such actions, and maybe the presence of the forts is why these usurpers ruled for the time they did 260-296AD.
There are/were 10 forts on the Saxon shore, spanning from Brancaster in north Norfolk right along the coast down to Portchester castle near Portsmouth, and all were connected by signal stations running right down the coast. Our fort (I will call it Burgh castle as Gariannonumn, which the fort was originally called, is a bit of a mouthful) is located just to the SW of today's Great Yarmouth, near the rivers Waveney and Yare. As you can see from the picture the coastal landscape was very different 2000 years ago and this was a crucial factor when deciding where to place the fort. The great estuary where Yarmouth is today (I can’t help but think the river Yare had a say in the name of great Yarmouth, i am sure you can see the links?) was a massive opening into Britain, trading vessels could bring goods in from all over the Empire, also goods could be shipped out, and any Roman province without connection to the rest of the Empire was doomed.
As well as a great advantage for trading vessels it was also a great entry point for seaborne raiders, they could slip in and penetrate deep into Britain, raid and loot unprotected sites and slip out again as silently as they came in. Caister and burgh castle would have acted like a gateway to this great estuary, protecting the local shipping with its own naval fleet and the armies units garrisoned in the forts. The roman army was the most efficient of its time, it was well organised in administration and on the battlefield, they would have had standard operating procedures (SOP’S) just like the British army have today, it is doubtless to say that when word arrived of trouble inland the forts garrison would act decisively and quickly to deal with the issue, they may even have had a quick reaction force (QRF) who would burst from the forts at the first word of trouble, ahead of the main force they could locate and track the enemy. Burgh castle was designed to house 500 cavalrymen and their horses, or 500-1000 foot soldiers, so you can imagine how they could pose a considerable threat to a small inland raiding party. There are accounts of the ‘Equites Stablesiani’ (a class of cavalry from the late roman army, consisting of 15-20 units) being garrisoned there in 395AD, they could very well have been the last roman unit to be stationed at the fort. Despite Romes military prowess she was beginning to learn in the latter part of the 4th century AD that she was not the unbeatable force that had previously dominated the ancient world, in the year 367AD Picts from Scotland, Franks and Anglo Saxons from Germany launched almost simultaneous attacks, they penetrated deep into Britain and it was not until 369AD that the barbarians were pushed out and order was restored in roman Britain, for a time at least.
Well that was just a brief little detail into the reason for the forts construction and how it was used to help defend the empire. Next time I will concentrate more on the fort itself in-depth, its defences and what came with a fort in Roman Britain.