It occurs to me that I don't give reality enough credit. Here I am, quietly impressed by Total War: Attila's fire simulation. And yet, if a real fire broke out, I'd attempt to put it out without once thinking, "wow, reality has excellent dynamically propagating fire effects."
The trailer shows how the upcoming Total War will handle assaults against settlements. A big part of this is the escalation of sieges. Storm a city straight away and it'll be harder to take. Wait it out in a protracted siege and, when you do decide to start the assault, the city will be decaying—thus easier to breach.
For the defenders, though, barricades can be placed. These can be smashed through, but doing so will take time. It's often easier to go around, but this gives the defending general the opportunity to funnel the enemy into a trap.
For more on Total War: Attila—including details of its planned campaign map improvements—check out my hands-on impressions from last month's announcement.