Besieging, I would expect :
- historical fortresses (bastions, glacis, star fort, etc.)
- fortifications : trenches, ravelins, ditches, curtain walls, etc.
- tactics : parallel trenches, surrounding, mining, sorties, etc.
- equipment and soldiers : siege artillery, mortars, sappers, etc.
But I don't know how we would play four-month sieges in a couple hours !