Diplomacy

In Civilization 4 every AI leader holds one of five attitudes toward you (Friendly, Pleased, Cautious, Annoyed or Furious), with the reasons shown when you hover over its name, and trades techs, resources, gold, maps, cities and agreements such as Open Borders, Defensive Pacts and Permanent Alliances. Warlords added vassal states, Beyond the Sword colonies and the Apostolic Palace, and the United Nations can award a Diplomatic Victory.

Diplomacy in Civilization 4 turns on each rival leader's attitude toward you, one of five levels (Friendly, Pleased, Cautious, Annoyed and Furious), which decides how willing that leader is to trade and how good a deal you get; hovering over a leader's name in the score box shows the attitude and every reason behind it, per the base game's manual (pp. 99-100). On the trade table you can exchange technologies, resources, gold, maps and cities, sign Open Borders, Defensive Pacts and Permanent Alliances, and make peace. Shared religion and a leader's favorite civic raise attitudes, while war, a different religion and refused demands lower them. Warlords added vassal states, Beyond the Sword added colonies and the Apostolic Palace, and the United Nations can end the game with a Diplomatic Victory, covered on Victory Conditions.

Rendered view of a tall rectangular office tower of glass with a low building in front, a line of colored flags on poles and white clouds. — A wonder scene from 2K's Civilization IV page: a tall glass slab building behind a lower hall and a row of flags, under a blue sky. Firaxis Games and 2K

Quick facts

Attitudes	Friendly, Pleased, Cautious, Annoyed, Furious
Opening talks	Foreign Advisor (F4) or a click on the leader's name
Tech trading	Needs Alphabet on at least one side
Deal types	Immediate (gold, maps, techs, peace, cities) or annual (resources, gold per turn, Open Borders, Defensive Pact)
Annual deals	At least 10 turns
Peace treaty	At least 10 turns; a cease fire has no minimum
Vassal states	Warlords; peaceful vassalage needs a master with Feudalism
Colonies	Beyond the Sword: overseas cities split off as a vassal
United Nations	Mass Media, 1,000 hammers; elects a Secretary-General and votes on Diplomatic Victory
Apostolic Palace	Beyond the Sword: a Medieval wonder like the United Nations, votes weighted by faith

Source: Civilization IV manual, pp. 99-106; Warlords manual, pp. 12-14 and wonder chart; Beyond the Sword manual, pp. 23-24, 27.

Leader attitudes

Each AI leader forms an opinion of you from how great a threat you are, whether you have fought, whether you allied with its enemies and whether you keep your word, and the base manual (pp. 99-100) sorts that opinion into five attitudes, from friendly to furious. A friendlier leader trades more readily and on better terms; a hostile one may still trade at "a stiff price". A very angry leader, most often one at war with you, may refuse to talk at all for some turns.

The reasons are listed as pluses and minuses. GameSpot's walkthrough names the pluses as Open Borders agreements, staying at peace, sharing a religion, adopting the leader's favorite civic and trading, and the minuses as war, a different religion, sharing a border, dealing with the leader's enemies and refusing requests such as gifts. Enough minuses, it warns, and the leader declares war. GameSpot's 2005 review noted that the AI leaders remember refusals.

Every leader has a personality and an agenda. The manual says warlike leaders usually will not trade anything of military value and knowledge-focused ones chase advanced techs. Each leader's traits and favorite civic are on Leaders.

Religion and civics

Religion was added partly to give diplomacy a motive. Soren Johnson, the lead designer, wrote in his afterword (p. 181) that earlier Civ games made it feel "quite arbitrary" which civilization liked you, and that a different State Religion from a neighbor's may lead to animosity and war, while missionaries in a neighbor's largest cities can win "a long-term ally". GameSpot's walkthrough calls religion "one of the largest factors in diplomacy" and suggests signing Open Borders with a neighbor that has no religion yet and sending missionaries. The religions are on Religions.

Many leaders also have a favorite civic and may press you to adopt it: Johnson's examples are Gandhi with Universal Suffrage and Mao Zedong with State Property, per the afterword (p. 182). Leaders form their own friends and enemies, he adds, and often demand that you join them in a war or an embargo, so trying to please everyone "may leave you with no friends at all". You can also ask another leader to switch to your civics or religion as part of a deal. The civics themselves are on Civics.

The trade table

The trade table lists your tradable items on one side and the other leader's on the other; selecting items on both sides makes an offer, per the base manual (pp. 100-101). Asking for something while giving nothing is a demand for tribute, which may be refused and usually lowers the leader's opinion; giving something for nothing is a gift, which leaders never refuse and which often raises their opinion. Items in red will not be traded.

Trade items come in two groups that never mix: "immediate" items (lump sums of gold, maps, technologies, peace treaties and cities) and "annual" items (resources, gold per turn, Open Borders and Defensive Pacts), which last at least 10 turns and can be ended earlier only by war, per the base manual (p. 102). The full list:

Item	Kind	What it does
Gold, lump sum	Immediate	Any amount
Gold per turn	Annual	Owed even with an empty treasury; units are disbanded to pay
World map	Immediate	Both sides see what the other has explored
Technology	Immediate	Learned at once
Resources	Annual	All its benefits pass to the receiver; the giver keeps them only if it has a second source
Open Borders	Annual	Free movement and trade routes into each other's land
Defensive Pact	Annual	An attack on either partner brings in the other; void if either partner attacks anyone
Permanent Alliance	Immediate	The two share resources, techs, maps and victory or defeat
Declare war on a third civ	Immediate	Usually costly to ask
Cities	Immediate	Rarely given up unless under great duress
Peace	Special	At least 10 turns; tradeable only for gold or technology
Cease fire	Special	No minimum; nothing can be added to it
Change civics or religion	Immediate	The other side switches to match yours

Source: Civilization IV manual, pp. 102-104.

Some items need a technology first. Technology can be traded only once at least one side knows Alphabet, per the base manual (p. 102). GameSpot's walkthrough lists Writing for Open Borders, Paper for map trading, Currency for trading gold, Military Tradition for Defensive Pacts, and Communism or Fascism for Permanent Alliances. Trading resources needs both capitals connected; see Resources.

Open Borders, Defensive Pacts and Permanent Alliances

Open Borders let each side's units move through the other's land and use its roads, and extend each side's trade routes into the other's cities, which pay more than domestic routes, per the base manual (pp. 63, 103). Missionaries need them to enter foreign land. Without Open Borders, entering another civilization's borders is an act of war, and declaring war on an Open Borders partner sends both sides' units home.

A Defensive Pact makes each partner declare war automatically on anyone who attacks the other, and it is canceled if either partner attacks anyone. A Permanent Alliance goes further: the two civilizations become "one nation with two rulers", each keeping its own units and cities but sharing resources, technologies, maps and victory or defeat, with a declaration of war or a treaty by one binding the other, per the base manual (p. 103).

War and peace

Declaring war is "the polite way to open hostilities", and a leader you refuse may ask for a counter-offer, end talks or declare war on you, per the base manual (pp. 100-101). A peace treaty empties each side's units from the other's land and lasts at least 10 turns; a cease fire does the same but either side may declare war again at once, per the base manual (p. 104). Using nuclear weapons brings heavy diplomatic penalties, per the base manual (p. 135), and a failed spy mission tells the victim who sent the spy and can start a war. Fighting the war is on Combat.

Vassal states (Warlords)

Warlords lets one civilization become another's vassal, per the Warlords manual (pp. 12-14). The master gains extra happiness across its empire (the vassal gets some unhappiness), passage through the vassal's land, sight into all its cities, healing there as fast as at home and use of its fortifications. The master may demand any of the vassal's resources, even its only one, and a refusal ends the agreement in war, the only way the two can come to blows. The vassal joins its master's wars and cannot declare war or make peace by itself.

There are two kinds of vassalage. In peacetime a civilization can offer itself as a vassal to a stronger one that knows Feudalism, and may leave after 10 turns; anyone at war with either side is then at war with both. In wartime the same agreement is a capitulation, which the vassal cannot break unless it grows to more than half the master's land and population or loses half of its own land since signing, per the Warlords manual (p. 13).

Vassals count toward victory but cost money. For score and victory the master gets credit for half of the vassal's land and population, and the vassal keeps the other half; the master also pays more maintenance for its own cities, more as the vassal's cities grow in number, which the manual warns "may drag your economy to a halt". See Economy and Warlords.

Colonies (Beyond the Sword)

Beyond the Sword added overseas maintenance, a cost on cities on a continent without your capital that grows with their number, and colonies as the way out: granting those cities Colony status splits them off at once into a separate civilization that becomes your vassal, per the Beyond the Sword manual (pp. 23-24). The manual leaves the details to the Civilopedia's "Colonies" entry under "Beyond the Sword Concepts".

The United Nations and the Apostolic Palace

The United Nations is a world wonder (Mass Media, 1,000 hammers in the Warlords manual's chart); once it is built, a Secretary-General is elected and can call votes on resolutions from time to time, one of which is "Diplomatic Victory", and the winner of that vote wins the game, per the base manual (p. 106).

Beyond the Sword added the Apostolic Palace, a Medieval-era wonder that works like the United Nations "but with voting power determined by one's faith rather than one's size", per the Beyond the Sword manual (p. 27). Steam's Beyond the Sword page says it gives "a way to win a diplomatic victory earlier", and GameSpot's May 2007 preview described its builder pushing decrees that stop followers of the same religion from attacking one another. The manual leaves its resolutions to the Civilopedia; see Beyond the Sword.

Frequently asked questions

How do you improve relations in Civ 4? In Civilization 4, leaders like you more for Open Borders, peace, a shared religion, their favorite civic and trade, and less for war, a different religion, a shared border, dealing with their enemies and refused requests, per GameSpot's walkthrough. Gifts are never refused and often raise a leader's opinion.

What are the AI attitudes in Civ 4? Civilization 4 leaders are Friendly, Pleased, Cautious, Annoyed or Furious toward you, and hovering over a leader's name in the score box lists the reasons, per the base manual.

How do vassal states work in Civ 4? Vassal states arrived in Civilization 4 with Warlords: a weaker civilization can offer itself to a master that knows Feudalism, or capitulate in war, then follows the master into its wars and must hand over resources on demand. The master counts half the vassal's land and population for victory but pays more maintenance, per the Warlords manual.

What does Open Borders do in Civ 4? In Civilization 4, Open Borders lets each side's units pass through the other's land and extends trade routes into foreign cities, which pay more; missionaries need it to enter. It is an annual deal lasting at least 10 turns, per the base manual.

What does a Defensive Pact do in Civ 4? A Civilization 4 Defensive Pact makes each partner declare war on anyone who attacks the other, and it is void if either partner attacks first, per the base manual. GameSpot's walkthrough says Military Tradition allows it.

How do you win a diplomatic victory in Civ 4? In Civilization 4, build the United Nations (or, in Beyond the Sword, the earlier Apostolic Palace), then win the "Diplomatic Victory" vote that the elected Secretary-General can call, per the base manual.

When can you trade technologies in Civ 4? In Civilization 4 technology trading opens once either side of the deal knows Alphabet, per the base manual. Technologies are immediate items and can be traded only for other immediate items such as gold or maps.