Why would be anyone attack a castle? Why not just go around it,

>>1475479
Castles are often place in strategic locations such as a mountain or river passing. Also enemy forces inside the castle can use it as a base of operations and harass the enemy army while fleeing back to the safety of the castle when needed.

Castles hold the ability to deploy, house and coordinate troops through some sort of leadership that would take up residence in the castle.

You can't just simply leave a body of hostile men in a place while you go past.

>>1475479
If you go around you're just opening yourself up to attacks from it, especially since you likely don't have a castle to hide in.

>>1475479
The knights inside would be able to harrass you while you marched and retreat back to the castle if you tried to fight back.

Ideally you don't. You just stop supplies getting in until the defenders have no choice but to either surrender or starve

>>1475504
which takes years

The castle lets them hit you in the ass while you attempt to forage for food, you might try and starve them out, but they can starve you out as well. In those days food supplies were one of the biggest military limitations.

>>1475504
>castle = full of supplies for a small band of knights
>an army on the run = need constant replenishing of supplies for a huge force away from home
Good luck starving out the castle.

Usually armies beseiged castles, not attacked them. Sometimes it took years, usually it took a lot less. Usually armies only attacked if they had some massive advantage and there was some larger drawback to besiegements.