Part 31: Mechanics: How to deliberately destroy a city

Simple Answer:

Cities are destroyed when they would be reduced from size 1 to size 0.

City size is ALWAYS reduced by 1 when conquered. For cities without City Walls, size is also reduced by 1 whenever a defender in the city dies.

Therefore, you will destroy any size 1 city that you conquer. You can also destroy cities without conquering them (which is generally bad since it means no stolen tech, etc.) by killing a defender in an unwalled size 1 city.

Under normal circumstances you will therefore destroy any unwalled city which has a number of defenders greater than or equal to its size -1. And you won't destroy any others except City Walled size 1 cities.


What about when that's not good enough though?


Complicated Answer:

There are many things which can reduce a city's size from numbers greater than 1 down to 1, but there are only a few things that can reduce size below 1 (and therefore destroy a city). They are:

1) Starvation. This only really works in theory. A city that has a negative Food surplus will drain its Food box by that amount every turn. When the box hits 0, Settlers are disbanded and Food Caravans are canceled. If there is still a deficit, there is generally one turn of warning and then the city shrinks by 1. It may well shrink again the next turn and so on until its Food surplus reaches 0 or above or the city is completely destroyed at size 0.

In principle you could use this to destroy a city that you conquered and don't want. However, in practice it's usually impossible. The trouble is that a size 1 city only consumes 2 Food per turn and that even if you turn all citizens into Entertainers or whatever, the city tile itself will still always be worked and will usually produce 2 Food minimum. You can therefore only starve-destroy a city that was built on a Desert, a Forest, a Swamp, a Jungle, a Mountain, or a Glacier because those are the only terrain types that give 1 or less Food. And even the AI isn't dumb enough to build on those most of the time.

2) Building a Settler. This reduces population by 1. If it would reduce population to 0, you get a message asking if you really want to do it. If so, the city is destroyed. Note that your capital will never actually be destroyed in this manner; it will just remain at size 1. That is sometimes handy for quickly building Settlers at the start.

The Settler will be supported from the nearest city (which may disband the Settler in short order if that city can't afford the Food price). However, if the nearest city is more than 10 spaces away, the Settler will be supported for free instead. This same rule about getting free-support units if the nearest city is far away also applies to acquiring units by bribing them or finding them in huts. Very useful at times. And in theory you could save on support costs in the long term by building Settlers, walking them out a long way from all your cities, building new cities with them, and then having those cities disband themselves by making Settlers which will be support-free.

Anyway, this is basically your only option for getting rid of a city that you already acquired and don't want.

3) Conquering. This always reduces size by 1. So any size 1 enemy city will be destroyed instead of conquered. I've heard some people claim that on rare occasions they captured a size 1 city, but I've never observed this myself under any circumstances and don't really believe it. Edit: HisMajestyBob suggested and testing confirmed that size 1 cities which formerly belonged to you but were conquered by the enemy CAN sometimes be reconquered instead of destroyed. This is the only situation in which a size 1 city won't be destroyed.

4) Killing a defender. This ONLY applies to cities without City Walls. Also, it for some reason does NOT happen if you attack from an Ocean tile or with air units. So if you do want to take an unwalled enemy city more or less intact, you can do so by blasting it with naval units and the like.

A special thing to bear in mind is that this can destroy a city WITHOUT you ever owning it. That's generally quite bad since you don't get any gold, stolen techs, or other bonuses that you get even if you destroy a city while conquering it.

Also, this can happen to you if you foolishly try to defend a size 1 city against barbarians early on or something. Don't do that. Run all your military units out of the city so that they try to ransom it instead.


There are also several other ways to reduce population which will not reduce it below 1:

5) Inciting a Revolt/Subverting the city. This works just like conquest in most respects, but you can use it to take size 1 cities intact (very handy sometimes) and also more of the city's improvements are likely to survive.

6) Poisoning the Water Supply. You can only do this with Spies, so it's not an option most of the time but each water poisoning does reduce city size by 1.

7) Nuking it. This cuts city size in half whether it's done with a Nuclear Missile or a Spy.


So, generally speaking, you need to use a combination of these techniques to set up for method 3 (conquest) or method 2 (building a Settler). Nukes and Poisoning the Water Supply are pretty much the premier tools for reducing population. Heck, that's all Poisoning the Water Supply does in the first place. But of course you can't do those till very late.

Typically the fastest way to reduce population is to kill loads of defenders in an unwalled city. You can theoretically destroy City Walls by having Diplomats or Spies do "industrial sabotage" a bunch of times. The issue with this method though is that if the number of defenders equals or exceeds the city size, you'll never get to conquer the city at all. The sweet spot is for the city to have 1 less defender than its city size. That way you conquer it, get the stolen tech and free gold, and THEN the city is immediately vaporized.

In order to bring this sweet spot about, you can use Diplomats to investigate the city. If the number of defenders is less than the city size minus 1, there isn't much you can do. Kill them all and the city will be left at size 2 or more. Conceivably the enemy will speed-build another defender next turn and you can kill that to reduce city size further. If they have too many defenders for their city size, you can kill some of them with ships or planes or Marines attacking from ships until they have just the right number. Or if they have too many defenders AND City Walls, you can kill defenders behind the City Walls until they have just the right number, then use Diplomats to destroy the City Walls, and THEN attack with your other troops. Or if they have too many defenders and don't have City Walls you could put a good defensive unit nearby and hope to lure them into attacking you and dying.

If you don't have any Diplomats around, you can't really get the intel you need to make this work for sure except by noting whether the city has a flag on its icon or not. Cities with flags have at least 1 defender, cities without have 0.

You may also be able to "siege" a city to induce starvation to get it down to the right size to finish off by killing defenders or conquering it. You'll just need to stand a unit on every single tile in the city's range that can produce any Food at all and keep them there turn after turn. Yeah, not really feasible.

Generally the most reliable and reasonably speedy method for destroying a city is to just conquer the thing, then have all citizens work maximum Production and minimum Food tiles while cranking out a settler. You should be able to starve it down to size 1 or 2 and then building Settlers will eliminate it completely.


However

This is a ton of effort and resources invested in order to not acquire a good thing. There are VERY rare circumstances in which I would rather destroy a city than take it intact.

There are only ever 3 potential downsides to owning a new city:

1) Unhappiness if you have too many cities and are in a happiness crisis at the moment already

2) Inability to found another city in a better tile right nearby

3) If the city is extremely vulnerable, the enemy may take it back and steal a great tech from you.

Under normal circumstances, none of those apply. Even when they do apply, they can almost always be mitigated. Meanwhile, owning even a lousily positioned city has tons and tons of advantages most of the time. It's especially handy to have cities in enemy territory to use as forward bases for healing and building troops and beginning settlement of the area.