附属国（也叫附庸）are countries that do not have the ability to perform their own diplomacy. Instead they have entered into an agreement with a more powerful country for protection: their Overlord.
Each kind of subject state is different but there are general guidelines all subject states must follow.
- Other than for Trade a subject can never enter into diplomatic agreements with other countries.
- When a country becomes a subject all their agreements with other countries are broken.
- The overlord and subject will always have military access to each others territory.
- Subjects have military access to the territory of other subjects of the same overlord.
- A subject can always leave a subject relationship by declaring war on their overlord.
- In addition most subject types will pay some sort of resource to their overlord, how much and which one will depend on the subject type.
- Requirements: These conditions must be true for this relationship to be possible.
- Payment: The subject makes this payment to the overlord on a monthly basis.
- Dip. slot: Whether a subject of this type contributes to the overlord's diplomatic relations limit.
- Join wars: Whether a subject of this type is automatically called into the overlord's wars.
- Integrate: Whether the overlord can integrate the subject.
- Break: Whether the subject can break the relationship.
- Limit dip.: Whether the overlord limits the subject's diplomatic interactions.
Currently, all subject types will be defended by the overlord when attacked.
游戏中最基本的附属国类型大概是朝贡国（Tributary）。This is a loose relationship where the subject is simply looking for protection in exchange for tribute. Unlike most other subject types the subject can at any time cancel a Tributary relationship, the only risk being that the former overlord will get a Casus Belli for the slight on their honor.
藩属（Feudatory） is a state that has obligated itself to follow the lead of a larger and more influential country in the same culture group. Historically these are countries that would often have been part of some sort of League with their overlord’s other subjects, in many ways this is a privileged subject type, if one with large obligations.
Feudatories provide manpower to their overlord and are expected to take part in their wars. Historical examples are the Roman Socii, the Punic cities of North Africa under Carthage or the city leagues in Aegean under the Antigonids in Phrygia.
附属部落（Vassal Tribe） is a Tribal Kingdom, Chiefdom or Federation that has a close relationship to a nearby stronger Civilized state. For the Tribal State this means a significantly easier route towards civilizing, as it will increase both the countrywide level of Civilization and the growth of it in all their cities.The Tribal state in turn pays with its manpower to the overlord who will also promise to protect them. Historical subjects of this type would be the Numidian kingdoms to Carthage and various states on the border with Rome.When a Vassal Tribe adopts a civilised form of government it will instead become a Tributary.
仆从国（Client State） are in some ways more tightly integrated with their overlord, but unlike the Feudatories they are not necessarily of the same culture and they don’t enjoy a privileged status in the same way. Client States will in most cases be the result of a war. A client king is separated from a governor mostly by his level of autonomy and having local ties to the ruled country.
总督领（Satrapy） are a special type of subject that is only available if the junior party belongs to the Persian Military Traditions. A Satrap is in some ways similar to a governor but is expected to have greater authority, bigger obligations, and a more imposing realm. As having powerful Satraps is an expectation in the east a few of them will also help with maintaining the Legitimacy for their overlord kingdoms.
Satrapies are notoriously independent minded and troublesome. Events will periodically require interacting with to keep Satraps happy.
Each subject has a Loyalty value to its overlord. This value will modify how much payment is actually sent to the overlord and at low loyalty they may also join Rebellions and Civil Wars against the overlord.
Subject loyalty is a value between 0 & 100, where 100 signifies total loyalty.
Below a loyalty of 50 a subject state is considered disloyal:
- This reduces what it pays to overlord by up to 50% (at 0 loyalty)
- If a rebellion happens of this culture the subject will join that revolt.
- If a civil war happens and a state is disloyal it joins the revolting side.
Loyalty is affected by the relation between subject and overlord, by the comparative army size of the overlord and its subjects of the same culture, the comparative population size and by things like laws, and the Overlord’s Aggressive Expansion, Tyranny and Stability.
It is possible to integrate vassals except for tributaries. It requires that the vassal has an opinion of at least 190 with its overlord. The time and cost of integrating a vassal depends on the size of the vassal and the diplomatic stance of the overlord.