Urban warfare is a puzzling thing. Every large city seems to have similar features--a central area with large buildings surrounded by smaller buildings of varying density that consist mostly of houses. Fighting in such an environment favors the defender, but attrition costs are incredible the most effective tactic is to engage in a "bleeding retreat."
Towers of ilium is curious about how warfare in an American city could be conducted from both angles. Would a spread out city like Los Angeles favor a defender more than a compact city like Boston? Perhaps it comes down to natural obstacles, in which case the Charles River would be the primary strategic impediment to both besieger and defender.