"What do you mean it depends? What does it depend on?" The terrain, your avaiable forces and equipment, the morale of your soldiers, the main goal of the opera

"What do you mean it depends? What does it depend on?" The terrain, your avaiable forces and equipment, the morale of your soldiers, the main goal of the operation, the short, mid and long term plans. Outside reactions. Strength of enemy. Outside reactions, will the enemy get more support if X happens or less, will it matter if key target is achieved before time Y, ... There is no magic bullet for something as complex as urban warfare. If you want to level all, just use a nuke. But there seems to be reasons, why that is not a valid option. If you go with lots of ground troops, you will have casualties. Here the question how much is acceptable to your own population. If you go fast, you achieve a different effect then going slow. Etc. Etc etc.