Norman West : Death of Robert Guiscard : The Turks
I now Bryennius was holding Castoria, as told above, so the Emperor who was eager to drive him out and regain possession of the town, called up his whole army again and after fully equipping them with weapons necessary for a siege and also those for engagements in the open he took the road leading to the fort. The situation of the town was as follows: there is a lake called Castoria, into which a promontory runs, which widens out towards the end and terminates in rocky hills.
On this neck of land towers and connecting walls were built in the shape of a camp, hence the town’s name of Castoria. On arrival the Emperor thought it would be wisest in the first place to made an assault upon the towers and walls with his battering-machines. But as it was impossible to get the soldiers near the walls except from a definite base, he first made a palisaded camp, next built wooden towers and bound them together with iron bands and then from these, as if from a fort, he commenced the battles against the Franks.
The siege-engines and catapults he drew up outside the town and then by day and night he fought and broke down part of the walls. However, the besieged resisted most determinedly (they did not surrender even when a breach had been made in the wall) so the Emperor, seeing that he could not achieve his object in that way, conceived a plan which was both daring and clever. It was to put some stout-hearted men into boats and make war from both sides simultaneously, that is, from the land and from the lake.
