(This page is for Classic ruleset. For Combat in the Multiplayer ruleset click here.)
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A unit cannot enter a square occupied by an enemy unit, and when directed to do so will attack instead, locking the two units in combat until one is destroyed. Also, a unit that moved next to an enemy can be auto-attacked that very moment if corresponding server option is on and certain conditions are met. An attack usually costs the aggressor one movement point, but results in no actual motion — the surviving unit remains where it was when the combat started. Bombers spend all of their remaining movement points when they attack, which gives fighters a chance to intercept them.
Some restrictions upon warfare are rather obvious — units must have a nonzero attack strength to attack, while defenders with zero defense strength lose immediately. There are also limits upon which units can attack which others. Land units can only attack other land units. Ships can attack not only other ships, but any land units adjacent to them (submarines are an exception and cannot attack land units). Helicopters can attack land and sea units and can be attacked by any kind of unit (land, sea, or air), at any time. Bombers and missiles can attack anything on land or sea, and though their targets will defend themselves from attack, they cannot attack the bomber in return. Only fighters can attack every kind of unit.
Note that aircraft within cities and air bases are on the ground, and thus vulnerable to land attack. Ships in port are similarly vulnerable. Note also the special ability of marines to attack targets from aboard ship; other land units must disembark before engaging enemy units.
There are two other actions related to combat. A unit ordered to sentry remains in place indefinitely and no longer asks for orders each turn. Sentry units can not only be reactivated manually (by selecting them), but activate automatically should an enemy unit come into view. Land units can additionally be ordered to fortify, which means they spend one movement point preparing to be attacked; once fortified they enjoy the same advantage as land units within an unwalled city. A unit whose movement points are exhausted cannot fortify — it must have one movement point left at the end of a turn to begin the next turn fortified.
Instead of combat, you may also harm your enemies with diplomatic actions.
Each unit begins combat with one or more hit points, which are the amount of damage it can sustain. (See the units page for how many hit points each unit starts with, and for the other combat statistics discussed on this page.) Combat consists of successive rounds of violence between the units, which cannot be interrupted and cease only when one unit is reduced to zero hit points and dies. In each round one unit succeeds in wounding the other; the damage a unit inflicts with each blow is called its firepower.
Which unit inflicts damage on any given round of combat is random. The attacker has a chance proportional to his attack strength, while the defender's chance is proportional to his defense strength. For example, archers (attack stength 3) attacking a phalanx (defense strength 2) will have a 3/5ths chance of inflicting damage each round, with the phalanx having the remaining 2/5ths chance. But there are many factors which affect a unit's strengths, which are all summarized in the table below. Notice that many bonuses are possible for defenders, but few for attackers, aside from veteran status; an attacking unit can mostly expect circumstance to work against it.
The normal adjustments to combat strength are as follows:
|General Combat Strength Modifications||Ruleset parameters (location may vary by rulesets)|
|Unit is a veteran at 1st level (veteran)||x1.5||units.ruleset: veteran_system.veteran_power_fact or unit_*.veteran_power_fact|
|Unit is a veteran at 2nd level (hardened)||x1.75|
|Unit is a veteran at 3rd level (elite)||x2|
|Defender strength adjustments|
|Terrain offers defense multiplier m||xm||terrain.ruleset: terrain_*.defense_bonus [in %]|
units.ruleset: unitclass_* with flag="TerrainDefense"
|Terrain includes a river||x1.5||terrain.ruleset: extra_*[with flag="Natural_Defense"].defense_bonus|
(bonuses from all such extras are summed)
|In city with SAM battery against aircraft (except helicopter)||x2||effects.ruleset: "Defend_Bonus"|
|In city with SDI defense against missile||x2|
|In city with coastal defense against ship||x2|
|In city with city walls against land unit or helicopter (except howitzer)||x3|
|Land unit in fortress||x2||terrain.ruleset: extra_*[without flag "Natural_Defense"].defense_bonus|
(bonuses from all such extras are summed)
in most rulesets, uses yet another "Defend_Bonus" effect
|Land unit fortified or in city **||x1.5||units.ruleset: unit_* without flag "Cant_Fortify" with unitclass_* with flag "CanFortify"|
terrain.ruleset: terrain_* without flag "NoFortify"
i Since v.3.1: effects.ruleset: "Fortify_Defense_Bonus"
** Land units able to fortify get a 1.5x "automatic fortified" bonus in a city, regardless if fortified or not. This rule will be unhardcoded since v.3.1.
These factors are combined: Each factor that qualifies as true is multiplied into the final bonus. Thus, a city built on a hill with a river that has city walls is very hard to conquer. Note that fortified units receive no extra bonus in a city: being in a city already gives them a "free fortify bonus." Also, since v.3.0 some units can fortify just not to wake up on passing enemies but never get the bonus.
There are also combinations of units and circumstances that result in very specific adjustments to combat:
|Specific Combat Modifications|
|Pikemen attacked by horsemen, chariot, knights, or dragoons||Defense strength x2|
|AEGIS Cruiser attacked by an aircraft, missile or helicopter||Defense strength x5|
|Fighter attacks a helicopter||Helicopter firepower reduced to 1|
Helicopter defense strength x1/2
|Ship attacked while inside city||Attacker firepower x2|
Ship firepower reduced to 1
|Ship attacks land unit||Both have firepower reduced to 1|
Green units have a 50% percent chance of becoming veterans each time they survive combat (33% for hardened and 20% for elite), which gives them greater strength in all future engagements.
Units remain damaged after losing hit points in combat, and will enter subsequent engagements with this disadvantage. Damaged land and sea units also begin each turn with fewer movement points than normal, in proportion to what fraction of their total hit points remain (but not less than the class-specific minimal speed). To regain hit points they must spend turns neither moving (on their own, may be transported or even change transports without changing a tile) nor attacking (destroying the target, bombardment does not count). Resting in the open restores 10% rounded up of the full hit points (unless the unit belongs to a class losing HP); spending a turn fortified adds to the restoration the same value for any unit that can fortify; and in a city they regain never less than a third part (rounded down) of their original points. Additional to the basic and fortified regeneration goes the effect "HP_Regen": in a fortress they regain one-quarter of their original hit points, for cities see below the bonuses for specific buildings. The United Nations wonder restores another two points per turn to all of your units, it's a "Unit_Recover" effect. A unit in the game can never get more than its type full hitpoints or have less than one hitpoint.
If you sentry a damaged unit, it will become active and request new orders after its hit points are fully restored.
You may enhance the effects of resting in a city for your and allied units with several different buildings:
|Restore 100% for Land units|
Stack kill, Cities and Forts
When several units on the same square are attacked, the unit most capable of defense protects the entire square. More precisely (see
get_defender() in the code of
common/combat.c), for all defenders on the field which can defend against the attacker winning chance is calculated to the precision of 0,001%; if top result is similar for several units, unit cost is taken into account (forth goes the cheaper one), and if even then there is uncertainity, the units are rated by (defense strength)×(rounds it is able to lose)×(firepower).
If the defenders are within a city or fortress, the loss of that defender leaves the other units intact; but outside of such fortification, loss of the defender results in the loss of every unit in the square (can be turned off by 'killstack' server option but in most rulesets it is an uncommon practice). For that reason, if a Leader unit presents in the game, he always goes the last to defend a city but in open field will defend weaker units. Less surprising is that when a ship carrying other units is involved in combat (as either attacker or defender), only the ship participates in the engagement and its occupants are lost if the ship goes down.
Defeating a unit inside a city without walls kills one citizen if the attacker is a land unit (but it does not destroy size 1 city). Once the last defender has fallen you may enter the city and claim it as your own with either a land unit or helicopter; ships and aircraft can assault cities but not take them. In the process of the capturing the city loses 1 population which destroys city of size 1. Upon the capture of a city from another civilization, each building has a one-fifth chance of being destroyed, and the victor may discover a technology held by the vanquished.
Building a fortress requires the construction advance. To begin construction, move settlers, workers, or engineers to the location at which you desire a fort and give them the build fortress order. The work will require only three settler-turns. A fortress can stand anywhere outside of a city.
There are several buildings which enhance the strength of units which are attacked while inside the city:
Nuclear missiles do not engage in combat like other units — they either strike within range of an SDI Defense and are harmlessly destroyed, or detonate and blast the entire 3x3 area centered on the unit or city they attack. Within the blast area all units are destroyed, cities lose half their population, and each land square has a one-half chance of becoming polluted with fallout.
Just as excessive pollution across the world can trigger global warming, fallout raises the chances of nuclear winter with the opposite effect — rather than coastlines becoming jungles and swamp, terrain begins changing into desert and tundra. Settlers, workers, and engineers must be given the clean fallout command to dispose of nuclear waste, which costs three settler-turns per square.
Bombardment is a special combat action accessible for some units (with "Bombarder" flag up to v.3.0, will be unhardcoded later) in some rulesets under certain conditions. Since v.3.0, it can be directed on any tile around the bombarder in bombard_max_range ruleset setting (defaults to 1, but can exceed the bombarder's vision). Rules of bombardment:
- The bombarder must have nonzero bombard_rate (also, obviously, nonzero attack).
- All units and/or city on the bombarded tile must belong to players at war with bombarder's owner.
- i 'Up to v.2.6:' target tile is a land tile.
- i 'Up to v.2.6:' the bombarder is not transported.
- target tile has at least one unit on it (can't bombard an empty city).
- The bombarder loses no hp.
- The bombarder loses all movement points.
- Each of the units on the bombarded tile is bombarded and may take damage.
- For each bombarded unit, combat with bombarder happens with all usual effects and bonuses but for attacker's bombard_rate rounds (i.e. maximal possible damage to a single defender is attacker's bombard_rate*firepower).
- No bombarded unit is killed by bombardment (will always have at least 1hp left).
- If a city is bombarded and attacks of the bombarder kill citizens in it, it loses 1 population, but only over 1 (i.e. a city can't be destroyed by bombardment).
- A bombardment may cause an incident (i.e. provide casus belli for a future war).
Also, if ruleset setting force_capture_units and capture is possible, you can't bombard the target. In Civ2civ3 ruleset, attack of Bombers, Stealth Bombers and Helicopters have bombardment attack against land units (helicopters have normal attack against sea units).
Note that on some older servers you can bombard a tile with inaccessible units only (e.g. Helicopter vs Helicopters). It results in losing your movement for nothing.
Actions alternative to combat
Newer versions of Freeciv have actions which are not combat but are applied to hostile units by your ones.
This action makes enemy units with the flag "Capturable" yours when performed to them by your adjacent unit with the flag "Capturer". All units on a tile must be capturable; if the tile is a city center, the captured units bounce around. Action doesn't succeed if it would result in you having more then one unique unit. Successful capture takes single capturer's move point.
Your unit spends one move, and an enemy's unit finds itself in his owner's capital (must currently exist, or deportation fails) with no movement points.
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