Treaty

Treaties are the diplomatic agreements between two Empires, which set up the possible ways of interactions (known as Diplomatic Abilities in the tooltip) between the two. The Treaties Tab of the Diplomacy Screen lists all Treaties occurring between your two Empires. You can propose new Treaties here or break/downgrade existing Treaties.

There are 4 categories of Treaties:

• Trade, Treaties defining what Resources can be bought and sold and what tariffs are applied to these exchanges;
• Information Sharing, Treaties restrict how much strategic intelligence is shared between the two Empires;
• Border Policy, Treaties defining how open your Empire's borders are to others' beliefs and military forces;
• Military Accords, Treaties which constrain military interactions between the Empires' Armies.

Treaty Mechanics

Negotiating Treaties

• Once two Empires meet with each other, both can propose new Treaties to the other Empire everyturn.
• For Treaties proposed by others, one can either Accept, Counter, or Refuse.
  • Once a Treaty is Accepted, one can immediately propose another Treaty in the same turn. It is possible to negotiate all the possible Treaties in the same turn using this method.
  • Counter means asking Money in return for accepting the Treaty. If you don't have enough Money, the Treaty can only be refused.

• If a Treaty is Refused, the Empire is not able to propose any other Treaties in the same turn. The Treaty negotiations will only open up again in the next turn, with an Influence cost on the refused Treaty. Only after 5turns can one propose it again without any cost.

• When two Empires meet for the first time, all the Treaties will be the most basic ones, as the default diplomatic status. Higher level Treaties will have a larger benefit, while keeping certain agreements of the basic Treaties.
  • Accepted Treaties can improve the Attitude of the other Empire.
  • Alliance can open up more advanced Treaties.
  • Not actively negotiating new, positive Treaties can deteriorate the Attitude of the other Empire.
  • Liege-Vassal relationship has a special set of Treaties (see below) that will apply automatically.
    • If the Vassal is freed, all the Treaties between the two Empires need to be renegotiated entirely.

• Every signed Treaty will decrease both Empires' War Support equilibrium by 5. This means both Empires are a bit less likely to go to war with each other.
  • If all the pre-Alliance Treaties are signed, both Empires' War Support equilibrium will be down to 25.
  • Signing Alliance will also decrease the War Support equilibrium by 5.
  • If all the Alliance Treaties are signed, both Empires' War Support equilibrium will be at 0.
  • Note that Militarist Cultures will always have a +30War Support, which can override the Treaty/Alliance equilibrium.

Breaking Treaties

• Breaking Treaties or refusing Treaties too many times will deteriorate the Attitude of the other Empire, and cause their War Support to increase.
• Downgrading or breaking Trade Treaties can force certain trade routes to stop, lead to extra Grievances.

List of Treaties

All the possible Treaties under normal circumstances are listed below, with basic Treaties listed higher and advanced Treaties listed lower.

When two Empires meet the first time, the 4 base Treaties (Forbid New Trade, Reveal Capital, Closed Borders, and Tolerate Skirmishes) will be automatically applied as the default state; only advanced Treaties need to be negotiated.

When signed an Alliance, the first level of Alliance Treaties will be signed together automatically.

Trade	Information Sharing	Border Policy	Military Accords
Forbid New Trade No new trade exchanges can be set up by either Empire. Existing Trade Routes are unaffected. Trade Routes also cannot cross into the other Empire's Territory, and must take a detour.	Reveal Capital Both Empires accept the other's ambassador, revealing the position of their Capital City.	Closed Borders Armies are unable to directly enter Territories attached to the other Empire's Cities. Exchange of ideas and beliefs between the Empires is limited. Moving Armies into other's Territory will cause "Trespassing" Grievance. Units with the "Stealth" trait can always trespass despite the Treaty limitations. Expansionist Cultures can always trespass despite the Treaty limitations. Their Units won't suffer trespassing Health penalty, but the Grievance still apply.	Tolerate Skirmishes Attacks within the other Empire's borders are strictly forbidden. Skirmishes in neutral Territory may not immediately lead to war. Attacking other's Army will cause "Attacked Me" Grievance. Trespassers will also be attacked.
Only Trade Luxuries Empires can only trade Luxury Resources between each other. All the Luxury Deposits of the other Empire will be revealed on the map. This is usually the very first Treaty that AI will propose, and the very first Treaty that AI will likely accept.
Trade Everything The Empires can trade both Luxury and Strategic Resources. All the Strategic Deposits of other Empire will be revealed on the map.	Share Maps Both Empires share their geographical knowledge with each other. Both Empires' exploration on the map of will also be shared.	Open Borders Armies can travel through the other Empire's Territories, except within City walls. Beliefs and ideas are shared freely. Religions and Influence will be normally spread under this Treaty. Armies are still not able to enter urban Districts under this Treaty.	Non-aggression Pact Aggressive actions of any kind between the Empires are entirely forbidden. Both Empire's Military Units cannot attack each other anymore.
Alliance Level Treaties
Cheap Trade The buyer benefits from discounted access to this Empire's Resources. The seller still gains the same amount of Money. Both buying and transporting costs are discounted.	Share Vision Military intelligence is freely shared between the Empires. Both Empires can see the visions of each other's Armies, useful for spotting for allied artillery.	Open Cities Armies are able to go beyond the other side's City walls without penalty, including military Districts.	Tactical Cooperation The Empires' Armies can regenerate and pay for repairs while in each other's Territories. Armies in allied Territory will receive Supplied Status.
Free Trade The buyer benefits from free access to this Empire's Resources. The seller still gains the same amount of Money. Both buying and transporting a resource are free of charge.	Scientific Agreement Empires share Vision. Technologies researched by one Empire provide progress to the other Empire's research of that same Technology.	Cultural Agreement The Empires' Ideological Proximity improves gradually. Includes Open Cities agreement. The Ideological Proximity will rise and stabilize at a higher level.	Shared Logistics Units can be upgraded while within each other's Territories. Empires share their transport infrastructure. Train Stations and Airports can also be used by allied Armies.

Vassal and Liege Treaties

The Liege-Vassal relationship has a special set of Treaties:

• Share Resources: Access to Strategic and Luxury Resources is shared between the two Empires. No trade is necessary.
• Share Vision: Military intelligence is freely shared between the Empires.
• Control Beliefs: The Liege Empire defines the State Religion of their Vassal. The Vassal's Influence contributes to extending their Liege's sphere of influence rather than their own.
• Control Foreign Policy: The Vassal Empire's diplomatic relation are entirely defined by their Liege; the Empires' fates are now intertwined.

Treaties during a War

In a war, all the Treaties will be ignored, and replaced by a special set of Diplomatic Abilities in all 4 categories of Treaties:

• End Existing Trade: All trade agreements are declared null and void; existing Trade Routes between the Empires are destroyed.
• No Information Sharing: No geographic or strategic information is shared between the Empires.
• Disregard Borders: Neither Empire respects the other's borders, so Armies can cross them freely.
• Open War: Empires are free to engage each other regardless of where their Armies are situated.

In addition, first showed in Stadia Opendev, then implemented in full game, there is another level of Diplomatic Ability above the Open War, called Mutually Assured Destruction:

• Mutually Assured Destruction: No holds are barred any more, as the Empires are able to launch weapons of mass destruction on each others' Cities. This madness will not end well.