Diplomatic Contact[]

To diplomatically engage requires a unit next to a nation's units or cities. This allows Cease-fire and Peace pacts. The time period you can engage after contact is seen by typing /show contactturns. All other deals require a diplomat or spy to enter a city and 'Become Ambassador' to establish an embassy.


An Embassy gives permanent intel on tax rates, treasury gold, technologies, wonders, government type, and foreign relations. An embassy allows making deals such as: trading gold, technology, shared vision, maps; and forming an Alliance.

To engage in diplomacy you must:

  • Go to the Nations tab to select the nation with whom you wish to engage.
  • Click the Meet Player button.
  • Using the menus, decide what you wish to give and receive (see pacts).

If an AI player is not cooperating, you can often find out why by attempting a Peace or Alliance with them.


See also Diplomatic actions

With Diplomats and Spies, you can observe and manipulate other civilizations more subtly than by military means. Both units are fragile and must move cautiously to survive. Aggressive diplomatic actions can spark a diplomatic incident, giving a nation Casus Belli. Courthouse, Police Station, and Supreme Court offer some protection against aggressive diplomatic actions. Theocracy resists a hostile espionage embassy and requires you both to agree to Cease-fire or Peace first.

Three actions can be done by done to a lone enemy unit (these actions cannot be attempted on a stack of units):

Bribe Unit[]

Most foreign units can be bribed with gold to join your nation. Bribing can only be done to units alone on their tile, although other diplomatic units do not count toward this—they will instead engage in diplomatic combat with the unit trying to bribe their compatriot. It is not necessary to be at War to bribe a unit, but it does cause a diplomatic incident, which gives the victim a casus belli against you. Bribe cost depends on several factors:

  • increases with wealth of the enemy civilization;
  • increases with the enemy unit production cost and veteran level;
  • decreases with loss of enemy unit hitpoints;
  • decreases with increased+ distance from enemy capital;
  • half cost if enemy unit is non-military.
  • double cost if enemy unit is a ship
  • other factors:

Sabotage Enemy Unit[]

A Spy can sabotage an enemy unit, reducing its hitpoints by half if successful. Sabotage can only be done if at War. It requires the victim unit to be alone on its tile, although other diplomatic units do not count toward this—they will instead engage in diplomatic combat with the unit trying to sabotage their compatriot. After successful sabotage, a spy returns to the nearest domestic city.

Spy Attack[]

Spies can engage in diplomatic combat in the open field against other Diplomat type units. This can be useful for eliminating an approaching diplomat from a hostile nation.

Actions done to cities:[]

Diplomatic units can do actions to cities also. The base odds of success for diplomatic actions on enemy cities vary, though most are between 70% to 85% (see Diplomatic Operations.) Base odds can be reduced by defense bonuses such as those from a Courthouse or Police Station.

  • Except for Investigate City, Diplomats can attempt only one diplomatic act, after which the Diplomat unit will be spent. Spies can select actions which may survive the mission.
    • Names of Diplomatic Operations will either have the word "Escape" after them or not. This indicates if the action has the expectation of survival if successful.
  • Enemy Diplomats or Spies will oppose hostile actions with Diplomatic Combat. If you die, the mission fails. If the enemy dies, you lose a movement point, have a chance of promotion, and can try again if you have moves left.

The actions available upon a city are:

Establish embassy[]

Diplomats and Spies always succeed when asked to establish an embassy. An embassy gives you permanent contact with that civilization and the ability to make deals beyond Cease-fire or Peace. The chance of success for this operation is 100%, though it is disallowed if you are at War and the city has a Police Station or the nation is Theocratic.

Investigate city[]

Investigate City is the only diplomatic action that can also be done by non-diplomatic units: Tribesmen, Explorer, and Satellite. Only Spies are able to Investigate City while still loaded on a Transport: to do so, use the "D" (Do) command.

When you Investigate City, your unit gives a report on the city's units, buildings, income, and what it is producing. There is an 85% base chance of success. These odds are reduced by half for nations with the Mausoleum of Mausolos and for cities with Police Stations. (Nations with the Democracy government do not get the Investigate City resistance bonus from Police Stations.)

  • Discovery: Prior to doing the Investigate City action, there is a 20% chance of being discovered in the attempt. The consequences for discovery are: (1) The target nation will become aware of it, (2) be given a casus belli from a diplomatic incident, and (3) any diplomatic unit gets a chance to eliminate the investigator in diplomatic combat.
    • Regardless of being discovered, surviving units will proceed to do the investigation.

Sabotage city[]

Sabotage is an attempt to destroy a building or the current production in a city. Diplomats select at random, but Spies also have the option to choose a specific building or the city's current production with Targeted Sabotage (which has a reduced chance of success.) Palaces and Wonders can't be sabotaged. Fortifications, City Walls, or any building in a capital have half the chance of success. Sabotage is only possible if at War. If successful, a Spy returns to the nearest domestic city.

Industrial Sabotage[]

Same as above, but your unit attempts to destroy what a city is currently producing.

Steal Technology[]

Your agent attempts to steal blueprints for a tech. A city can only be stolen from once by Diplomats, who steal blueprints for a random tech. Spies can steal more than once, but the city becomes more resistant each time. Spies can target a specific tech, but targeting reduces the chance of success. Theft may be attempted when not at War, but causes a diplomatic incident. A successful Spy is returned to the nearest domestic city.

  • No tech theft in cities with 50% Foreign Nationals. Cities with foreign populations of half or more are conquered war zones. They have not yet domesticated scientific infrastructure. Diplomatic tech theft is not possible from such cities, though they are not immune from theft by conquest.

Steal Map Fragments[]

Steals a portion of the world map of the target nation, giving you vision of fragments of their world map. The fragments are not "regions" but rather a "spattered" revelation of the nation's entire map. Base odds of success are 70%.

Incite Revolt[]

For a large amount of gold, a foreign city will betray its governing nation and change allegiance to join your nation. The city's size will be reduced by 1. The incited city brings along all nearby home-units that the city supports. Home-units in foreign cities remain in the enemy's control. Units outside cities are lost to both players. Incitement may be attempted even if not at War, but causes a diplomatic incident. This action can't be done to capital cities nor to any cities under a nation which has the Mausoleum of Mausolos. Many factors influence the price of treason:

  • cost is ½ if the city was originally yours
  • cost increases with city size
  • cost increases with wealth of the enemy civilization;
  • cost is 3× against Democracies;
  • cost is 2× against Theocracies;
  • cost is 3× for natively founded cities under Nationalist government;
  • cost is ⅓ for non-native cities under a Nationalist government;
  • cost is -33% if the city is not currently owned by its original builder;
  • decreases with greater distance from an enemy capital;
  • increases with the cost of present units;
  • increases with the cost of the buildings present in the city;
  • cost is ½ if city is empty of units;
  • goes up/down with the happiness/unhappiness of individual citizens;
  • cost is ½ if the city is in revolt OR the enemy civilization is in anarchy;
  • cost is 2× if the city is celebrating;
  • increases by 2× if city has a Courthouse or the nation has the Supreme Court:
    • increases by another 2× if the city is occupied and protected by Courthouse or Supreme Court.

Treason's cost is complex! The only sure way to know is to make a diplomatic unit inquire how much the potential traitors want.

Poison city water[]

Only a Spy can commit this atrocity, and only in War; it empties the city granary and kills one citizen. A successful spy returns to the nearest domestic city. A size 1 city will be eliminated by this action.

Tile Claim[]


Claims a tile as the sovereign territory of your nation.

  • Can be done to any tile in your own national territory by a single Diplomatic unit.
    • Prevents a growing foreign city from claiming the tile.
  • Can be done to a non-domestic tile if:
    • it is adjacent to another Tile Claim
    • your Diplomatic unit is supported by the presence of another unit on the tile
  • An unoccupied Tile Claim will be claimed by any foreign Land unit that enters the tile.
    • Casus Belli is triggered by 1) Making a Tile Claim on a Foreign tile, or 2) seizing a foreign Tile Claim through occupation.
  • To do a Tile Claim:
    • Select a diplomatic unit on a tile that can be legally claimed (see above).
    • Do ('D') >> (select tile) >> Build Tile Claim.

Diplomatic Combat[]

In Freeciv, mechanics for diplomatic and military combat differ. Odds of success are calculated in a three step process. First, odds of success start with a 50% chance of success. Second, this chance is modified by additive bonuses or subtractive penalties applied for each unit, resulting in the base chance. Third, the base chance for the aggressor's success is proportionally reduced by percentile defense bonuses.

Step 1. Starting chance of success: 50%

Step 2. Additive modifiers: these add or subtract to create the base chance. Aggressor adds these to base chance of success; defender subtracts these from base chance of aggressor success.

Additive Bonuses
unit is a Spy 25%      
Veteran Level bonus

Diplomat title

Spy title
not veteran 0% attaché informant
veteran 1st level 10% V1.png secretary handler
veteran 2nd level 15% V2.png envoy agent
veteran 3rd level 20% V3.png ambassador operative
veteran 4th level 25% V4.png emissary secret agent
veteran 5th level 30% V5.png statesman neutralizer
veteran 6th level 35% V6.png plenipotentiary spymaster

Step 3. The odds of aggressor success are proportionally reduced by a percent:

Other Defense Bonuses
  bonus*                  x̄ odds**
in city protected by Courthouse 25% -
in city protected by Homeland Security 25% -
in city with Police Station 25% -
in city with Palace 50% -¼
in city with Ecclesiastic Palace 50% -¼

* bonus = the percent of the base chance that is reduced.

** x̄ odds - the "real effect" on final odds, if under an average base chance of 50%.

Example: A v1 Spy attacks a v2 Diplomat in a city with Police Station.
   1. Starting Chance of aggressor success = 50%
   2. Base Chance: 50% (start) + 25% (spy) + 10% (v1) - 15% (defender is v2) = 50 +25+10 -15 = 70

= 70% base chance

   3. Defense bonuses:      25% (Police Station):      70% - (25% * 70)   =   70% - 17.5%  =  52.5%

Final odds   =    52.5% chance of success

Diplomatic Operations[]

Assuming there are no defending diplomatic units to get through (see Diplomatic Combat, above), then each Diplomatic Operation has its own separate base chance of success. The only thing that can modify this base chance of success are defense bonuses. The type of unit does not matter, nor does the veteran level. The table below gives the base odds of success for each type of diplomatic operation:

Diplomatic Operation Odds
 operation odds
Investigate City **85%
Sabotage City † 80%
Steal Technology *80%
Incite Revolt 80%
Poison City 70%
Steal Map Fragments 70%
Targeted Tech Theft *64%
Targeted Sabotage 55%
Steal Map Fragments and Escape 55%

After you have your base odds for your operation, you calculate final odds by reducing any applicable defense bonuses. If the reduction shows a "-" sign, simply subtract this number from the base odds. In the case of sabotaging city walls, the base chance is simply halved:

Raw Defense Bonuses
 operation reduction
City has Courthouse - 20%
City has Police Station ** - 20%
City has Homeland Security - 20%
Sabotage on any Building in a capital city × 50%
Sabotage on City Walls × 50%

* A targeted tech theft requires succeeding twice. In other words, if odds were 80%, then 80% × 80% = 64%.  (If the city had a Courthouse, then 60% × 60% = 36%, etc.). Tech theft cannot be done to any city that has 50% or more foreign nationals, as it is considered a war zone under martial administration.

** (1) Investigate City has a 20% chance of being discovered, which does not affect the odds of the operation. A discovered operation causes a diplomatic incident, which notifies the targeted player and gives any defending diplomatic unit a chance at diplomatic combat. If the operation is not discovered, the enemy will not get a report of it. (2) Normal defense bonuses against Investigate City do not operate. The only bonuses are: Police Stations half the odds of Investigate City for all governments except Democracy. The Mausoleum of Mausolos also halves the odds for all units except Satellites. (3) Satellites always have a 100% chance of operation success, no matter what.

Sabotage City gets a +10% higher chance of success if: (a) The saboteur is Theocratic, or (b) The city is foreign occupied and has foreign nationals inside it.

If a Spy is trying to steal from a city that has already been stolen from, the operation must succeed one more time for each time it was stolen from. So, for example, if a Spy is stealing from a city that has been stolen from twice, she must succeed three times (80% × 80% × 80% = 51%). If this is targeted stealing in a city with Courthouse and Police Station, she must succeed four times under lower base odds:  40% × 40% × 40% × 40% = 2.56%.

A Diplomat who tries to steal from a city which has been stolen from will always fail.

A useful bookmark is the full Diplomatic Action Chart which shows odds for every above possibility.


Players can make informal requests, agreements, and threats via in-game chat. To transfer actual property they must arrange a pact. This can only be done if the players have an embassy. Each player can build a list of items offered next to a list of what will be receive in return. These can include:

  • World Map, Sea Map. The nation's current world map or sea map— showing all the terrain discovered by that nation.
  • Technology. Teaches another nation a technology.
  • Gold transferred from one nation to the other, from the national treasury.
  • City transfer (except for capital cities.) This also transfers all home units supported by the city.
  • Shared vision — shares the vision of the nation offering it to the recipient nation: everything your cities and units can see as the game unfolds. This is a persistent ability: when you no longer wish the other nation to see everything, you must cancel this pact from the Nations Tab.
  • An Embassy.
  • An Alliance treaty.
  • A Cease-fire, Peace (requires only contact, not an embassy.)

To remove a treaty item from the pact list, double-click on it. Only when both players indicate 👍 satisfaction is the deal consummated.

Diplomatic States[]


This is the state of having no status at all: the nations have never encountered each other.


If two nations have met, the default state is War.

Unlike most other diplomatic states, War is declared unilaterally by one player on another; thus, declaring War only requires that you have already met the player once or he has declared war on one of your allies. To declare War on an opponent, cancel any treaties with that player until the War state is reached.

Only the War state allows one to attack a unit or to take a city.

In War, foreign units impose zones of control and cities can be incited to revolt with no disapproval from the senate.


A Cease-fire can be agreed, which entails no restrictions other than a lack of War. After 16 turns, it will lead back to the state of war. Be careful that reverting to a war state does not trigger consequences in the diplomatic states of allies and neighboring nations. You may renew and extend a Cease-fire before it expires. When a Cease-Fire has 3 or less turns left, you may create a new one, instead of being forced to wait for it to expire into war.

The first time you meet an AI player, it will always offer you a Cease-fire treaty.

Under representative governments, the Senate will block an unprovoked attempt to declare War again before the end of a Cease-fire; the only way to do so is to dissolve the Senate by revolution then break the treaty in the ensuing anarchy. (However, the Statue of Liberty allows you to break a treaty and restore order in the same turn.)

In this diplomatic state, units impose zones of control.


If you want Peace with a nation, you can sign a peace treaty. For a transition period there will be an Armistice. Like Cease-fire, it has a countdown of 16 turns, but unlike a ceasefire, ends up in the peace status when the time runs out.

This transition period allows time to move units that would be automatically disbanded under Peace if they were inside the other player's borders. The AI will always insist on some turns of Cease-fire, then Armistice, then Peace, and will use the Armistice to move its units out of the other player's territory.

Breaking an Armistice drops you to War. Under representative governments, the Senate will block attempts to nullify an Armistice unless there is Casus Belli.

In this diplomatic state, units impose zones of control.


A peace treaty may be a step towards an Alliance. Or, it might be a way to force an untrusted nation from entering your territory, knowing that its Senate will prevent such actions.

Peace treaties come into effect after 16 rounds of Armistice, if no incidents occur. A nation may wish to deliberately spark an incident to prevent this from happening.

When a peace treaty kicks in, all military units inside the other nations's territory are immediately disbanded. Military units cannot cross the other nation's borders without first nullifying the treaty in the Nations tab. Cancelling a peace treaty drops you straight to War. Be careful declaring Peace with a nation where military cooperation might be needed--you each will be unable to enter each other's territory, since that is considered an act of War, and under representative governments, the Senate will block an unprovoked declaration of War. A nation without a Senate can unilaterally ignore this, but not the player who does have it. Therefore, a player with a representative government only ties his own hands, when he makes Peace with a player who has an absolutist form of government. The above restrictions do not apply to any nation possessing the Statue of Liberty.

Peaceful units impose zones of control and can't be attacked.


Alliance treaties come with obligations. You won't be able to ally any player that is at War with any current ally, and vice versa. If one of your allies declares War on another, the Alliance with the aggressor is automatically broken.

In an Alliance, zones of control don't apply. Allied units can enter the same tile, city, or transport unit.

Breaking an Alliance drops you to an Armistice treaty, giving each player time to move their units out of the other player's territory before a new peace treaty kicks in and disbands units. Non-representative governments can further nullify the Armistice to a War, and/or then propose a Cease-fire.

Under representative governments, the senate will block an attempt to break an Alliance without provocation. An Alliance can be broken at will by non-representative governments or any nation with the Statue of Liberty.

Casus Belli[]

Casus Belli is "reason for war." If you do an action which gives a nation Casus Belli, they can declare War on you even if they have a Senate and are in a Peace treaty with you. Casus Belli lasts for 12 turns, unless the server setting casusbelliturns has been modified. If Casus Belli already exists when another Casus Belli is given, it adds +1 turn to the existing Casus Belli duration.

Excusing Casus Belli. You may forget or excuse Casus Belli by offering another Cease-fire or Peace.

International outrage. Under some conditions, a Casus Belli can cause international outrage, which gives the entire world Casus Belli against you. This may happen if you explode a nuclear device in foreign territory, or violate a treaty after the United Nations wonder has been built.

Casus Belli triggers:

  • The following actions will give a nation Casus Belli against you:
    • Attacking a nation's ally
    • Pillaging a nation's territorial tile, unless you are allies.
    • Stealing Maps
    • Stealing Tech
    • Bribing a unit
    • Capturing a unit
    • Sabotaging a unit
    • Inciting a city to revolt
    • Poisoning a city
    • Sabotaging a city
    • doing a Tile Claim on a tile in their territory
    • occupying a foreign Tile Claim with your units
  • Exploding a nuclear device:
    • ground zero in Foreign sovereign territory gives Casus Belli to the entire world.
    • ground zero in Domestic or Unclaimed territory does not give casus belli.
  • Diplomatic combat.
  • Making a road, railroad, quay, canal, maglev, sea bridge, or river in foreign territory, unless you are allies.
  • Building a Fort or other base in foreign territory, unless you are allies.
  • Transforming Terrain in foreign territory, unless you are allies.
  • Founding a City in foreign territory (by appropriating an empty Fort), unless you are allies.
  • Being discovered while Investigating a City, unless you are allies.
  • Moving military units in a foreign nation with whom you are at Cease-fire, Armistice, or Peace.
Previous: Combat Chapter Next: Government