Huge lag attacking Genoa (late campaign)

[Suthseaxe]

My game normally runs very smoothly and I have no issues with field battles and most siege battles (except for the walls falling animation, for some reason). However, I am attacking Genoa as Venice and I am unable to do so due to extreme lag. Does anyone know what may be causing this?

[Lifthrasir]

How many units do you have and how many units on the other side?
For example, if you have a full stack fighting another full stack in a narrow space, this might be due to the fact that the engine is not able to manage so many animations in such a space. But that's just one of the possibilities.

Have you also tried to play that battle with lower graphic settings, just to see if it helps?