In modern games, much of the focus of AI is on individual, agent-based decision AI - essentially "every man for himself". Some work has been done, of course, on multi-agent, squad-based AI as well. But what do you do when you are dealing with the siege of a castle that may pit hundreds of attackers against hundreds of defenders? A proper siege is a complex machine of roles, responsibilities, and reactions on a large scale. In this lecture, we will show the approach used in Total War: Warhammer to create the very specialized high-level AI to guide these massive armies in a way that provides a convincing, epic-scale battle, and yet also serves the design needs of the game. This talk will include topics ranging from general attack strategy through threat analysis for defenders. There wil lalso be a recap of the history of why many of the changes were made.