So, I'm doing some heavy research into knights and have come across lots of information about lance formations and the importance of knights in armies before infantry became the bread and butter of bulk forces. I'm also aware the sieges outnumbered open field battles (insert number) to 1. I also know that cavalry was rather useless during sieges since defenders were protected behind walls.
So, if stone walls detered knights on horseback, what made heavy Cavalry the go-to force in warfare during their time?
If standing behind a wall was the best defense you had, then what did defending knights do during a siege of not ride into battle beyond the walls?
If I'm looking to take over France starting from the Spanish border, how do I decide what I need to siege and what I don't?
If I'm a duke trying to rally my 40 something knights and their lances for defense against Spain, how do I go about defending my duchy from the assault?
So, if stone walls detered knights on horseback, what made heavy Cavalry the go-to force in warfare during their time?
They were great at smashing through lines, causing chaos, and outflanking large groups of infantry, not to mention the sheer intimidation factor. There are two types of sieges. The first type of a siege of a border fortification, which was merely meant to be a delaying tactic. They would hold out and simply wait for the larger army to arrive and lift the siege. Cavalry would obviously take part in the coming battle. The second type of siege is a besieged city, which was most likely the result of a catastrophic loss in the field, in which heavy cavalry probably played a major role.
If standing behind a wall was the best defense you had, then what did defending knights do during a siege of not ride into battle beyond the walls?
Defend the walls, police the civilians, plan tactics for a future battle, things of that nature. If they were landed knights and it was their castle being besieged, they would be responsible for resource rationing or possibly even negotiations for ransom or surrender. The whole point of a siege was to be a delaying tactic, as I mentioned earlier. Nobody wanted to make the Hollywood-style last stand unless they truly had to.
If I'm looking to take over France starting from the Spanish border, how do I decide what I need to siege and what I don't?
It's really up to you, but there are general logistics that need to be considered. Movement of your baggage trains and supply lines needs to be preserved, so any fortress that could hamper your movement or holds a garrison that directly threatens the flanks of your supply line probably needs to go. Armies often sustained themselves through pillaging the countryside, so if a castle holds large stores of food and weaponry, it might be beneficial to take it. Castles or cities that are especially wealthy could be good to besiege on the chances that you'll get a substantial ransom payment.
If I'm a duke trying to rally my 40 something knights and their lances for defense against Spain, how do I go about defending my duchy from the assault?
If you can stop them before they cross the Pyrenees, do that since they won't have time to really use their full strength. If you can't, and you're on the border, then you send riders to Paris to tell the king that the Spanish are coming and you need help, then you hold up in your fortress. If you are not on the border, you will likely combine your forces with either the royal army or a bunch of other dukes and counts and you'll march against the Spanish.