These units are the answer. With two movement points, they can venture into enemy territory and reveal defensive forces, while their extra tile of sight reduces the chances that they themselves will be spotted; and if they are, the Flanking promotion increases their chances of survival. Doesn't the AI have the same visibility over their territory that the player has then? Seems odd that you can be inside AI territory and the unit not be seen by them. Also the Flanking promotion is for attacking siege units isn't it? How is that promoting a scouting units survival chances? You can defend a city “passively” or “actively”. Of course the choice is partly related to how far in the game you are - in the mid/late game you often find even once you take a city down you are still surrounded by enemy culture, which tends to favour passive city defense for any initial counterattack. If the nearby roads all turn neutral as they will do in early wars, then active defense becomes much easier and many of the risks are removed - you can attack approaching stacks with any and all units needed with equal mobility. If it is his territory still your counter-counter attacks are slower and easier for the enemy to deal with and you probably should revert to turtling (i.e. everything on one square again asap). Of course the siege unit for active defense will be the catapult until pretty late on - without the extra city attack bonus the trebuchets are expensive and relatively weak to use in that role, except when no other choice is present. 3.2 PROMOTIONS The one extra thing I add to city attack stacks is one or two non-CR attackers - in case a stack comes up against units outside a city (often some reinforcements being sent from another city). Ideally at least one of these will be mounted, so the last attack that ends up on the defenders square can then jump back to the main stack. They can double up for mopping up nearly dead city defenders that killed some of your CR attackers, so they don't require an increase in overall stack size, you just end up with slightly less CR specialists. Of course these units can also help your active city defense force once the city is taken (or maybe they could be considered the same thing, just doing active defense before the city has even been attacked). So most of the units in a huge stack are likely to come away from a siege weapon’s attack without a scratch. Whereas if a siege unit attacks a small stack, they’ll all get damaged and may have to stop to heal. This is also why it’s a good idea to park your stack in one tile when attacking a city rather than spreading them out around it. Small stacks are best against siege weapons, if you have a stack of 7/8 or more, you maximise the damage a siege weapon can do. Having siege weapons hit everything would have probably made SoD a lot weaker tactic, but as it stands if you have stacks of 2-3 you will suffer limited damage from siege weapons. SoD tactics are to protect you against everything else - because of the mechanic that the best current defender is selected from a stack it means that attacks by mixed forces against a SoD are weak - two SoDs of equal size/tech/composition/promotions and the attacker loses badly (even absent fortify/terrain bonuses). The two threats a defending SoD has are a much bigger/better SoD, or a ton of suicide siege units followed by a similar size SoD attacking it. Of course the other weakness of a defensive SoD is strategic - you can only hold one square with it, meaning that it will have to attack/move some time to be useful.