I remember reading an account of a siege which seemed to imply that a siege tower was wheeled up to a wall for an assault and then stayed there for some time (like days/weeks) during the siege. I don't know much about this stuff but I always kind of thought once you wheeled it up it was sort of a now or never type situation. I find it difficult to imagine defending a tower that's 3 feet from the enemy for any length of time.
I also remember hearing about trebuchets knocking ramparts off the top of walls. If the attacker had more firepower than the defender, could they essentially clear the entire top of the wall before an assault? Would the attackers who scaled the walls be able to then just instantly take them? Did this happen often? While I'm on the subject: wooden hoardings in the era of stone castles seem like they'd be really easy to destroy. Any details about how useful they were?
Obviously I don't know much about this stuff but I'd like to know more. My final question is what books you would recommend about sieges, particularly during the middle ages.
I teach history and I can give some insights, but on medieval topics I'm no expert. Medieval sieges were a game of positions and long term planning.
On siege towers, here's the low down. Most of the time the defenders could watch them being built over the course of a week or two, naturally the idea would be to burn them. Therefore they had to be carefully defended at night against raids. Against fire during the assault, they would often have untreated furs layered over the exterior and soaked with water.
Yes, once it hit the wall it was often now or never. The group of men who crossed the bridge first were referred to as 'the forelorn hope' as they very rarely survived the battle. If the attack was stopped, often the towers were allowed to dry and then burned. If the weather was too wet, the defenders would cut the bridge between the wall and tower and let it stand, useless to both sides.
Trebuchets had great range, great accuracy, decent firing speed, but took a while to build and needed protection as well. The issue with the clearing the ramparts theory is that their projectiles were nowhere near the speed of modern ones, ie the defenders could move and protect themselves from the boulders fairly easily, and then step back to their posts to repel scaling attackers. Not to mention that while accurate in principle, trebuchets were made of wood and needed to be fine tuned according to humidity and changing weather conditions. This meant that no commander would keep firing his trebuchets once his troops got close to the walls, so no close cover for scaling attackers either.