To the OP. think of it like Rock/Paper/Scissors: Siege/Ranged Units crush Cities. Melee units slash Siege/Ranged Units (and they are defenseless against Melee) Melee units are useless against Cities (eventually Cities will wear Melee down) or.... Siege/Ranged crushes Cities Cites cut Melee Melee covers Siege/Ranged Really, when you talk a city, you should have a good mix of siege, melee, and ranged units. Make sure that you plan the attack so that all of the units that you want to use enter the appropriate tiles at the same time (because the city has a two tile range and it doesn't seem to get obstructed very often, so you don't want to give them free hits on you). Use your melee and ranged units to take out any units that they have, because you can't win the battle if they eliminate your units, and set your siege units up, and they can start firing against the city whenever they're ready. Once you get rid of all of their units, plant your melee units next to the city and let them dig in (click the shield to give them a defense bonus, and let them heal if necessary), and maybe hang one or two back if you have any extras just to make sure that you have to one to finish the job. Then let your ranged units join in on the siege. Don't forget to pillage when injured, it usually leaves you with enough moves to attack afterwards. In fact, if there's something for my melee units to pillage, I may let them take an early swipe and heal by pillaging. For an added bonus. If you steal one of their workers, you can have their repair what they've pillaged, and if the battle is protracted, you can pillage and get even more money!