Here is a reconstruction of the main gates at Maiden Castle. If you have been there, it is really impressive and you might wonder how these gates might be breached. Legio II probably made the final assault in less than an hour. No army ever has been so adept at this kind of assault. How could they have done this?
When the hill fort was first excavated by Sir Mortimer Wheeler, he was certain that there had been a major siege and battle here. 40 bodies were found and one has a ballista bolt in his spine. Do you see it? It is the first body and the bolt is labeled. Since then, there has been doubt about the siege. No more bodies have been found and there are no signs of siege works as you find say at Masada.
There are no siege works, though there must be some camps, because this was not a siege but an assault. Those in the fort were contained by their own walls. The Thracian Ala, only had to make regular patrols to keep the lid on and as this was not a siege, there was no need to close off the fort completely.
The only major work would have been to build platforms in front of the gate system for the artillery. With enough height, this could then sweep the gates and the opposing walls making it impossible for the defenders to defend directly. A cache of 20,000 sling stones, from the local beach, was found suggesting that the defenders could not use them. The supporting ballista fire made standing up a suicidal action.
Then the First Cohort of Legio II formed up in Testudo formation and took the inner rings and arrived at the gates where a covered ram could break in in minutes.
Here we come to the smart part of the plan. Vespasian's brief was to secure a safe buffer in the south of Britannia. Because this was an assault and not a siege, the rules of war allowed him to show mercy. The last thing that he needed was an angry local population. By showing that none of their defences, no matter how magnificent, could hold Rome back, he did not have to make unnecessary enemies by slaughtering everyone. The fact that the south was forever quiet after that showed the brilliance of his plan.
I think Wheeler's critics assume a siege. There is no evidence of a siege. So they assume that Maiden was not taken. But an assault is not a siege and there is evidence of an assault and its success and the mercy shown made the point that needed to be made.
Just to offer a sense of how effective the Romans were at assaults and siege work, let's consider Masada and Alesia.
The official line in Israel is that Masada was held heroically for three years. Current research suggests that the circumvallation wall, in stone, and the camps were built in maybe a week. That the ramp, built on top of a ridge and using lumber as a binding agent took 8 weeks tops and that the entire operation might have taken 4 months from start to finish.
At Alesia, according to Caesar's Commentaries, about 18 kilometres of 4 metre high fortifications were constructed in about three weeks. This line was followed inwards by two four-and-a-half metre wide ditches, also four-and-a-half metres deep. The farthest from the fortification was filled with water from the surrounding rivers. These fortifications were supplemented with mantraps and deep holes in front of the ditches, and regularly spaced watch towers equipped with Roman artillery.
Caesar ordered the construction of a second line of fortifications, the contravallation, facing outward and encircling his army between it and the first set of walls. The second line was identical to the first in design and extended for 21 kilometres.
Even with modern earth moving equipment, these efforts would take some beating. No army could did like the Roman Army. Remember their routine at the end of every 20 mile march day would be to build an overnight camp, before they had a meal or sleep. In the field this was done in full armour after carrying 70 pounds of kit all day.
With artillery support, assaulting Maiden's Gates was nothing to the First Cohort.
