City combat changes dramatically in Civilization VI, thanks to the new district system and the new rules for City Defenses. Having large, strategically important parts of the city outside of its main tile gives the attacker new possibilities for harassment, and forces the defender to carefully consider how they will defend against invasions. However, remember that the ultimate goal is still the central city tile: the City Center district.
City combat statistics[]
Cities are also considered combatants, and as such have combat statistics.
First, they have a Health (HP) stat, which is denoted "Garrison Health" and is double that of units (200 HP).
Second, they have a 
Combat Strength stat, which is used only for defensive purposes (that is, every time the city gets attacked). City Combat Strength is calculated in the following way:
- Base strength is equal to that of the strongest land or naval unit your civilization has built minus 10, or to the unit which is garrisoned inside the city (whichever is greater). Note that Corps and Armies are capable of pushing this number higher than otherwise possible for this era, so when you station a combined unit in a city, its CS will increase accordingly.
- Wall defenses add 3 CS per each level of Walls (up to +9 for Renaissance Walls); this bonus is lost if/when the walls are brought down. Note that this bonus is only valid for "ancient defenses" (i.e., pre-Urban Defenses Walls). If a city never built any walls and then got Urban Defenses, it will never get this bonus, despite actually having modern defensive capabilities.
- Each district the city has that isn't a Preserve or an engineering district (Aqueduct, Bath, Canal, or Dam) adds 2 CS, making more developed cities more difficult to conquer even without defenses.
- Bonus if the city is built on a Hill; this is the normal +3 bonus which is native to Hills.
- The
Capital gains an additional boost of 3 CS thanks to its Palace; this is called "Palace Guard" in the strength breakdown. - Victor the Castellan adds 5 CS to the city he is assigned to.
- The Bastions policy card adds 6 CS to all an empire's cities.
- A damaged district suffers a cumulative -1 CS penalty per 10% of its HP it loses (similar to units).
- A city-state receives +1 CS for each Envoy its Suzerain has sent to it.
As per combat rules, the damage the city will sustain from each attack is determined by the difference between the attacker's and the city's strength. Note, however, that the presence of City Defenses may greatly reduce that damage (see below).
Ranged attack[]
In Civilization VI, cities don't get to attack on their own unless they have built City Defenses. Once they have at least Ancient Walls, any city and its corresponding Encampment district gain a ranged strike with 
Ranged Strength equal to that of the strongest land ranged unit your civilization possesses (or 15, if no ranged units have been produced). Like in Civilization V, the city's ranged strike has a 
Range of 2, but unlike in Civilization V, it is subject to line-of-sight rules. This means that an attacking unit can now hide behind Woods or Hills, even if within firing range of the city. This also nets an additional combat advantage for founding cities on Hills, because they will enjoy a vantage point that allows them to fire over obstacles.
A city's Ranged Strength is not necessarily equal to its Combat Strength. It is instead always equal to the civilization's strongest Ranged Strength excluding air units, thus allowing a city's Ranged Strength to max out at 120 by simply building one Giant Death Robot. Thus it is possible for a city to be less effective (or more effective) with its Ranged Strike than it is when defending with its CS. It all depends on how advanced a civilization's ranged tech is currently, and whether or not it has Bastions slotted (which gives all cities a +5 Ranged Strength bonus).
Note that a city or Encampment cannot use a ranged attack against a neighboring city or Encampment. It is, of course, impossible for two City Centers to be two or fewer tiles apart; however, an Encampment cannot attack a City Center or another Encampment even if one is within its firing range. Stationed units, however, will still enjoy the invulnerability conferred by being in a City Center or Encampment, and be able to fire at the other (if they are ranged units, that is).
If the Outer Defense of a city (or an Encampment) has been completely destroyed, its ranged strike again becomes unavailable.
City defenses[]
Cities don't start with automatic defenses anymore...until you acquire the Steel technology. Before that, cities will be quite vulnerable to attackers: cities will only damage melee attackers in retaliation for their attacks, but ranged attackers will be able to damage cities with impunity (although they suffer a Ranged Strength penalty).
Building Walls in the City Center district improves its defense dramatically. Not only does it gain a ranged strike, but it also gains an "outer defense" perimeter (a.k.a. "wall"). This perimeter has its own health layer, which also defends the main HP by significantly reducing damage done to it (at least while it's still mostly intact, as explained below). But what's even more important is that the wall perimeter has different physical qualities than the main city - it is much tougher, practically impervious to most conventional attacks. This is expressed by a severe reduction of the damage normal units do to city defenses: -85% for melee attacks (melee, anti-cavalry, recon (Scout), heavy and light cavalry) and -50% for ranged ones (ranged, recon (from Skirmisher and above), air fighter, ranged cavalry). All naval units suffer from the same damage penalty as land units; however, naval ranged units (including naval raiders) do not suffer from -17 Ranged Strength when attacking cities like land ranged units. Only units with attacks that use 
Bombard Strength and certain early game support units may help breach city defenses, as you will see below.
The HP and quality of the defense perimeter depends on the level of the defenses: Ancient Walls have 50 HP, and each upgrade adds +50 HP, for a maximum of 150 for these so-called "old-world" defenses. In Gathering Storm the values are respectively +100 and +300. Not only that, but in Gathering Storm upgraded walls also gain engineering qualities which negate the effects of support units: the Battering Ram becomes ineffective against Medieval Walls and higher, while the Siege Tower becomes ineffective against Renaissance Walls and higher. This means that whenever a city builds Renaissance Walls, only units with Bombard Strength will be able to inflict full damage to its defenses.
Then comes the Steel technology, which acts as a kind of threshold to modern defensive capabilities, separating "old-world" defenses from "modern" defenses (a.k.a. "Urban Defenses"). Until that moment, each city has to build each level of Walls separately through the normal city production queue. After developing Steel, all cities acquire defenses automatically (without the need to construct Walls), and their HP goes up to 200 (400 in Gathering Storm). This means that an attacker facing a fully upgraded city will have to deplete 200/400 HP of Walls and 200 HP from the city to capture it.
Damaging city defenses[]
As mentioned above, most unit classes suffer a horrendous damage penalty when attacking any level of Walls. Ancient combat offers two units which may circumvent this penalty:
- The Battering Ram negates the penalty completely, but is only effective against Ancient Walls. Note that damage against the city itself is still subject to damage reduction from Walls, while these retain most of their HP. This will result in completely destroying the Walls before capturing the city.
- The Siege Tower allows attacks that bypass Walls and hit the city directly, inflicting damage as if there were no walls protecting it, but is only effective against Ancient Walls and Medieval Walls. Attacks will also inflict damage to the walls themselves, but with the damage reduction mentioned above. This may actually allow a city to be captured while its walls are still standing.
Akkad's unique Suzerain bonus confers the same ability as the Battering Ram, but against all levels of city defenses and against all cities (regardless of presence or absence of support units).
Note that both support units are effective for melee and anti-cavalry class units only. Ranged and cavalry units do not benefit from Battering Rams and Siege Towers (which takes care of the ridiculous notion of Horsemen operating a ram or running up the stairs of a tower). Akkad's bonus, too, works for melee and anti-cavalry units only.
Modern warfare completely negates the use of these medieval tools of combat - only modern weapons are effective against Urban Defenses.
Siege units (the ones which have the bombard-type attack) are specifically designed to bring down City Defenses, and always do full damage to them (and to cities in general). Also, units of the naval ranged and naval raider class do not suffer a Ranged Strength penalty against 
Districts but do suffer the penalty against walls. Worse yet, siege units with Observation Balloons and some later siege units are able to outrange city defenses.
There are also a number of 
Promotions which increase unit effectiveness when attacking cities or Encampments. These can be especially useful to a militaristic civilization bent on conquest.
The damage suffered by Walls themselves is calculated based on the city's Combat Strength compared to the attacker's Combat Strength (if melee) or Ranged Strength (if ranged, which for land units is also reduced). This means that, even if the attacker manages to do full damage to the wall, that damage will still be subject to the standard CS comparison, and, as seen above, a city's CS is almost always higher than the attacker's. This makes siege warfare something really difficult for the attacker without the proper tools. On the other hand, it also means that a technologically advanced nation attacking one which is 1-2 eras behind might be able to take cities even without the proper tools, simply by virtue of the much more advanced conventional weapons that it deploys: for example, Infantry attacking cities with 30-40 CS, even though they have Renaissance Walls, will still manage to breach the defenses by virtue of the big CS difference.
The presence of an outer defense also protects the HP of the city. While the walls are undamaged, no attack can harm the city itself (it will do 1 damage only). The strong protection holds until the walls' HP goes down to about 80% - the city will then suffer not more than 5-10 damage per attack. While they are "relatively" damaged (above 50% HP), attacks will get through and harm the city itself, but their force is still reduced. After the walls are "breached," and their HP falls below 20-30% of its original strength, the city starts taking real hits (that is, full damage).
Repairing defenses[]
Once damaged, the outer defenses of a City Center or an Encampment will not regenerate on their own. They have to be repaired from the Production queue of the city via the Repair Outer Defenses city project. This project, however, only becomes available once the city has stopped taking damage for three turns. The project repairs both city and Encampment walls over 1-2 turns (depending on how much damage was sustained and how much 
Production the city has), restoring HP and re-enabling Ranged Attacks.
While city defenses are damaged, you cannot build higher levels of Walls. For example, if your Medieval Walls were damaged during an attack, you cannot build Renaissance Walls until you repair the current walls.
Combat role of Encampments[]
The Encampment is a special District in more than one way - its denizens are more than capable of mounting a defense on their own against invading armies. Thus, an Encampment district will become impassable (even before it is finished), unlike other Districts, and will effectively turn into a second city resistance center with the following qualities:
- It has only 100 HP.
- CS similar to the parent City Center, excluding any bonus obtained for a Garrisoned unit.
- Defenses HP equal to the City Center (building any level of Walls in the city will supply both the City Center and the Encampment).
The Encampment fights independently from the City Center; that means that it will launch Ranged strikes on its own (while its Wall defenses are still up) and fight off melee attacks until conquered. This, of course, happens more easily because of its lower HP. When defeated (the Encampment's HP is brought down to 0), it and all its buildings are pillaged automatically. Unlike with other districts, the attacker doesn't gain any loot from doing so, other than relief from the Encampment's attacks. Also, its units may now enter and occupy the Encampment's tile.
Note that, like the City Center, the Encampment is capable of Healing at the rate of 20 HP/turn. This is an automatic action, which happens if its tile is not occupied. And, the moment the Encampment Heals some damage, its tile will become Impassable again, and enemy units will have to fight their way in again! This is a unique situation, which cannot happen with the City Center tile for obvious reasons (if an enemy unit enters the City tile, the city is conquered and switches hands). So, an enterprising defender could use this Encampment function to further confuse the attacking party.
Siege[]
A city besieged by Warriors
During an attack, the 
Citizens will constantly work to repair the damage to their cities. The city will automatically regain 20 HP per turn, but as mentioned above, damage to the walls cannot be repaired as easily. However, the word "siege" now acquires a brand new significance, because if the invading army manages to establish zone of control on all passable tiles surrounding the City Center, it will no longer be able to repair the damage it suffers, making it that much easier to defeat.
Pillaging districts adds a new layer of danger - pillaged buildings and districts have to be repaired from the city production queue, and this may take quite a few turns, depending on current Production capabilities.
Stealth units cannot besiege a city.[1]
Capturing cities[]
Finally, the way cities behave after being captured is also different from previous games. As before, a city is captured when its defenses and HP are brought down to 0, and when a melee unit enters its tile. The city loses part of its Population (but not exactly half as before, more like 1/4 of it), and all buildings in the City Center are damaged and need to be repaired before returning to full functionality. However, no buildings but the Walls are completely destroyed! These have to be rebuilt from scratch, if the civilization hasn't developed Steel yet; after that the walls must be simply Repaired from the production queue. In both cases the newly captured city is completely defenseless for a while. Note, however, that there is a special case when a city does retain some defenses right after being captured: this happens when the captor civilization has developed Steel, while the victim has not. In this case the captured city will have about 25% of its Defense HP (which more or less corresponds to the HP being added for Urban Defenses over Renaissance Walls).
The city is captured along with all the districts it owns, although because of Population loss, it may theoretically be unable to support that many districts anymore. Note that civilization-specific districts in a captured city revert to their generic versions (e.g., you can't capture a Greek city and enjoy its Acropolis); conversely, if a captured city has a generic district, which your civilization replaces with a unique one, this district will convert immediately. Special tile improvements don't convert - they simply disappear, along with any districts and improvements for which you have not researched the required tech or civic.
Any military units, ships and aircraft present in the City Center or Encampment are destroyed; any civilian units are captured (or at least those prone to capturing are). All Spies based there, including your own, will flee the confusion and relocate to their Headquarters.
Finally, unlike Civilization V, there is no "loot" when capturing a city. The victor won't receive any 
Gold; however, they will gain control of all Great Works that were in the city's buildings, districts, and wonders (except the Palace, which is rebuilt in the former owner's new 
Capital). If the city has any wonders, the conqueror will get the wonder's benefit if it is a long-term one (such as the yield bonuses from Petra), but will not receive one-time benefits (such as the free Great Prophet or Apostle from Stonehenge). Wonders under construction are cancelled, and their respective tile becomes empty - effectively, the losing side loses all the progress it had made towards this wonder.
Now the victor has to choose what to do with the captured city. Note that this choice doesn't need to be made immediately as before, but it does have to be made before the end of the turn - it appears in the Notifications tab and is required to end the turn. The options are:
- Keep city - This will immediately annex the city and its parent territory. The relevant Warmonger penalties apply. The city, however, enters "Occupied" status (see below).
- Raze city - This option will immediately remove the city and all its districts from the game. Note the "immediately" - unlike in Civilization V, a city won't take several turns to disappear. Its territory becomes Neutral again. Triple Warmonger penalties apply for this action. Also note that you can't raze Original Capitals, former City-States, and some other types of cities.
- Liberate city - This will return the city to its original owner, and is only possible if this city had been conquered by another player before. Liberating cities applies an Anti-Warmonger bonus, which will counter directly Warmonger penalty scores. If you Liberate a city-state, you will immediately gain 3 Envoys with it and become its Suzerain.
Occupied cities[]
Occupied cities work differently in Civilization VI. They are fully functional from the start (i.e., do not go through a "Resistance" period); however, their productivity is severely limited. First, they simply won't grow in Population, even when all the normal criteria for growth are met. Second, their 
Culture, 
Science and 
Faith output suffer a 75% penalty, while Production and Gold output suffer a 50% penalty. Finally, in Rise and Fall the city suffers a -5 Loyalty penalty per turn, which can be negated by permanently stationing a garrisoning unit inside.
A city will remain Occupied until its previous owner agrees to "Cede" the city through diplomatic negotiations (usually as part of a peace settlement), at which point the city will become fully functional again. Note that the previous owner will hold a grudge forever, though - this will sour your diplomatic relationship with them and their allies, until or unless you decide to return the city.
The city can also become fully functional again if the previous owner is eliminated from the game.
Strategy[]
City combat (in both offensive and defensive plan) can be divided into two distinct styles, determined by technology available: Ancient and Modern. The divisor is roughly the Modern Era, when the Steel technology makes ancient siege-support units obsolete, and when Flight introduces brand new ways to besiege a city.
Ancient siege[]
This is the time of close combat during sieges, as well as in general. In this period there are no ways to attack a city from outside its defensive range (unless you manage somehow to fully promote a siege unit and get the Forward Observers promotion, which grants +1 Range, but this is a very rare occurrence). This means that in order to assault a city, the attacking party will have to enter its defensive range and get exposed to constant fire from the city walls. What's more, the most effective units against walls - siege-class units like the Catapult - cannot attack and move in the same turn (again, unless they get a high-level Promotion). And, depending on the ranged strength of the city, siege units may get one-shotted, rendering their usefulness dubious.
Ancient defensive walls are a great obstacle: all units do very limited damage against them (with the exception of siege units, of course, and also ranged ships). It is entirely possible that a full army of land units, but without the necessary siege equipment, be destroyed while they hurl hopelessly against the stone walls, suffering normal retaliatory damage, but inflicting negligible damage on their own. But besides Siege units, there are also other, arguably more effective ways to overcome walls: namely, the Battering Ram and the Siege Tower support units. Having one of the two will remove the damage penalty your normal units suffer on either the wall or the city. Having both these support units will allow melee units to do full damage to both the wall and the city itself, while for ranged units only the tower counts. (All of the details above have been tested and confirmed by CivFanatics users.)
A Siege Tower is helpful if you plan to attack a city with melee units only. If you want to use other units in a siege attack as well you might want to build a Battering Ram instead. Normally, the wall must be torn down before the city can be attacked. It is generally done with the combination of melee, cavalry, naval, etc. With a Siege Tower, however, your non-melee units can focus on the enemy units, leaving the melee units to attack the city. Most importantly, this support unit is best suited for fast sieges (5 turns or less) because the wall is left standing and it will slowly whittle down your army (especially when the city is garrisoned). Once again, the Battering Ram is the slower but safer choice. Just beware of war weariness!
There are two scenarios where this strategy can work well. The first one is when a strong new melee unit is unlocked. Most of the time, their combat strength will be much higher than that of a city of the same era. If the enemy is behind in military technology, the only thing that can stand in your way is the wall, which is neutralized by the Siege Tower. The second scenario is when the enemy is of similar military might, but there are undefended cities. All other units can block the reinforcements while melee units make short work of the poor city. The city combat strength may be high, but attacking melee units have the advantage of numbers and the freedom to pillage.
Siege Towers can also prove useful during joint wars. If you and another player are attacking the same city, whoever reduces the city's HP to 0 will capture it. This normally means that both players laying siege to the city will try to stall until they can do enough damage to take the city in one turn, but this changes if you have a Siege Tower. Since the wall is left standing and only the city is at low HP, the other player cannot steal it from you without a Siege Tower of their own.
Of course, nothing of this will work against a determined defender with well-positioned defensive force; it becomes even worse if the city has an Encampment. Maneuvering in enemy territory at this time is difficult, which means that a few key melee units may block access to the city walls, while Ranged units pound the attacking force, destroying its key units. There is literally nothing the attacker can do in such case - just wait to research better tech and/or amass greater attack force.
Of course, there is always a trump card the attacker may use: a Great General. The General's aura will not only give an extra MP to a Siege unit, but also allow it to move and attack in the same turn (see the move-and-shoot rule). This means that, if you time your actions right (and have the physical possibility, of course), you can move several siege units in range and fire immediately, potentially eliminating the city defense in one fell swoop! From there on it becomes far easier to take a city. There is little the defender can do to prevent this, unless they are able to mount a preventative attack and take down the Siege units before they reach position.
Modern siege[]
When cities get Urban Defenses the main principle of city combat changes dramatically! The main battle for the city moves away from the city area itself and into the greater region. There are two reasons for that:
- Without the Battering Ram and Siege Tower, melee units become next to useless against city defenses again. And this time there is no replacing tech to remedy the situation - they will remain useless until the end of the game. Ranged units are a bit better, but they all lack the Range to fire from a reasonable distance - all but the Battleship, that is, and its upgrade, the Missile Cruiser. They are another story, as you will read below.
- Soon enough you acquire a number of long-range weapons, capable of firing from outside the city defensive range. First of these is the support unit Observation Balloon (and its later replacement, the Drone), which, although not a weapon per se, grants all other Siege-class units an additional point of Range. This works for the Bombard and all later units of the class. What's more, the Rocket Artillery has a range of 3 even without the Balloon (it doesn't have the Sight to match, though, so it will always need another unit to spot for it). Other units with a Range of 3 or more include the above-mentioned Battleship, as well as all aircraft (if you can build a base for them close enough to the city, or alternatively, move an Aircraft Carrier close enough). Bomber-class aircraft also inflict bombard-type damage, while the city itself cannot retaliate against their attacks - this makes them ideal for attacking cities!
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All these innovations allow players to attack from well beyond the defensive range of a city. If the defender doesn't have long-range weapons or units maneuverable enough to reach the attackers, there's absolutely nothing they can do to prevent sieges. Cue in all the latest cavalry-class units with terrible hitting power, some of which even specialize in taking out siege-class and ranged units. Cue in the defender's own aircraft, especially the fighter-class planes which are dedicated to fighting both air and ground units. Cue in all the defensive infrastructure (such as Forts) which any civ fearing for their life should've built well before the Modern Era.
Formations and the right unit combinations remain relevant in modern combat. Using the right support units under the right circumstances may mean both the success or defeat of any operation. You should always keep anti-air support units with your land and naval forces to defend them against fighter forays (regardless of whether they're defending or attacking); you should have Medics or the more-advanced Supply Convoys to improve unit survival chances in foreign lands when attacking; you should have anti-cavalry units close to your siege weapons - it may not prevent the attack itself (thanks to that amazing zone of control freedom cavalry has), but it will help ensure that they are not repeated.
Battles in modern times cover much more ground, thanks to a combination of longer-range units, faster-moving units (especially at sea) and infrastructure allowing very fast movement of armies at long distances. This makes defensive and offensive reconnaissance much more important in modern times than in ancient times; the attacking party should be able to identify the current positions of enemy forces and the weaker points in their defense, while the defending party should be aware of all gatherings of large forces, especially those featuring aircraft. And, of course, the ultimate threat: nuclear weapons!
Related achievements[]
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When Diplomacy Fails
Have a fully upgraded Giant Death Robot capture a city.
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Arabian Knights
Conquer a city with a Mamluk
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Investment Banking
Put a city under siege.
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Third Crusade
Playing as Frederick Barbarossa, conquer the city-state of Jerusalem
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Greatest Is As Greatest Does
Playing as Macedon, conquer a city containing both the Great Library and Great Lighthouse wonders.
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Resplendent Panoply
Possess all of the following after conquering a city in Conquests of Alexander: Hoplite, Saka Horse Archer, Maryannu Chariot Archer, Immortal, and Varu
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Big Bertha
In War Machine, reduce and capture a full-health city in a single turn.
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Rivals on Ice
Playing as Russia, conquer a city with an Ice Hockey rink
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