The castle which forms the principal setting for In the Company of the Dead is primarily inspired by Caerlaverock Castle in the Scottish Borders, but I modified it to suit my needs.
One of the modifications I made was to give it a second outer wall, my logic being that two walls allows you to pull back to the inner wall if you can’t hold the longer wall, and if you position them just so, you create a killing field between them with nowhere for the enemy to hide. That second wall is ruined in my book, so it’s indefensible, but it still impedes an enemy army as the wall is too structurally intact to march a force over it, and it’s within bowshot of the inner walls, so you risk heavy casualties trying to get over it or through the undefended gate.
So far as I recall, there was no inspiration for that wall beyond simple logic. I was a tactical genius. Then I discovered that actually someone thought of it before me.
These castles were called ‘concentric-ringed’ fortresses or castles, two of the best remaining examples being Beaumaris Castle and Harlech Castle in Wales. Both feature a second outer wall, although in both cases it’s only about 18 metres (60 feet) between the inner and outer walls, while in my castle, that distance is much larger – the idea having been that the space between could be used to pasture a small amount of livestock for food in the event of siege – but still close enough that anything within the wall is within bowshot. Harlech Castle also had a much larger wall extending down castle rock to the sea, complete with a water gate, to preserve ship access and resupply capabilities for the fortress.
Creating concentric-ringed fortresses meant that in the event the first wall was lost, the castle was equipped with a ready-built ‘coupure’ – a coupure usually being a ditch or palisade hastily-erected behind the castle’s main wall in the event of a breach, in order to better defend against an exploitation of the breach.
So much for my military genius.