One of the important aspects of diplomacy is getting tribute from the AI. Over the time I have done some research on this topic and I think there is enough interesting information to share.
The decisive factor for tributes is what I call Relative Military Strength (RMS). It is the result of 2 factors:
in relation to
Military strength of human player /Military strength of AI
The AI will give in to your demand, if your military strength is higher than the AI´s (RMS > 1 or 100%). If the military strength of the human player is equal or lower than the AI´s, the AI will demand tribute first and reject the human players demands.
The AI offers tribute for peace, if the military strength of the human player is 2 (200%) or higher (for modifications see the table under determinig tributes).
Sea units are counted if they are in a harbour on the same continent. Air units don´t have to be in a city but on the same continent. RMS is calculated at the beginning of the turn. Events during the tum (e.g. units land on AI continent, units lost) will will be taken into account next turn.
There is no tribute option under Republic and Democracy for the human player. Tribute can be demanded under all other forms of government (including anarchy). The AI demands tribute under all forms of government
Gold as a tribute is given only when the AI treasury has a minimum of 50g, otherwise you will always receive a tech (if available). The AI demands tribute only if the human players treasury has a minimum of 50g.
The AI will pay tribute only if a minimum of 8 turns passed since peace was concluded.
Obviously no tribute is given in a state of war. It may be offered for truce, though. In an alliance no tribute can be demanded. Instead gifts can be asked for.
Tributes are calculated. There is no random factor.
Multiplier: the multiplier for demanded tributes is 50g, for tributes offered for peace 100g.
Maximum tribute: of the AI treasury only full multipliers are considered, example: AI treasury 230g, multiplier 50g = max. tribute 200g
For practical purposes the following table might be helpful. It also shows the pattern.
Values are: Human players military strength/ AI military strength.
|REMS in %||values||offered for peace||paid when demanded|
A few examples:
It is relatively easy for the human player to get a higher RMS as the AI units are just counted by numbers. An extreme example: 2 warriors and one horse (sum of attack values = 4) are rated higher than 3 AI musketeers (number of units = 3) and tribute will be paid. If the AI is not willing to pay, you simply have to build a few more units and try again.
To get tributes from an AI on a different continent you can ship some units with a good attack factor there.
If your sea units (with an attack factor i.e. a trireme) are idle, they should wait in a harbour to improve your RMS.
It is also possible to get information about the approximate number of units the AI has from the tribute that has been received (or rejected). Example: tribute given is 200g, human military strenght is 15: the AI won´t have more than 6 military units on this continent.
If the AI offers peace it is safe to assume that the human player is stronger. If you expect to be at least 2 times stronger it is best to reject peace and then take the tribute offered for peace. You can demand tribute again the same turn you conclude peace (while the diplomatic screen is still open) and the AI will pay a full tribute again (assuming the treasury is not empty, yet). The 8 turn cycle (where no tributes are paid) begins in the next turn.