The possible treaty states, starting from the "lowest" are: War, Non-Intercourse, None, Non-Aggression, Subjugation, Protectorate, Trade Alliance, Trade & Research, Military Alliance, Partnership. (Capnq)
Treaties are only possible once you have made contact with another empire.
When contact is established, the initial treaty status starts out as "None".
You can trade with or conduct any other diplomatic operations (gifts, requests, etc.) regardless of the kind of treaty you have with another empire. The empire that you are at "War" with might not be willing to trade, but it is possible.
Some AI have a limit on the highest treaty to which they will agree. Nothing you can do will change this.
All treaties have cumulative effects which include the attributes of lower ones.
All treaties of Trade and higher are considered peace treaties for purposes of the victory condition "Peace for X years".
All treaties of Non-Aggression or higher prevent combat engagements.
Since the Military Alliance (MA) allows the ally to use your Resupply Depots, this can have some negative effects. The ally can now move throughout your empire and see what you have and if he is into colonizing in your systems, he can reach further. This can also be bad because if/when that empire declares war with you, his ships can be deep into your systems. A treaty of MA & beyond allows seeing other player's facility tags if you have that option turned on.
Regarding Protectorate and Subjugation, the offering empire will be the dominant empire. So a small, weak empire can dominate a larger one if agreed to. In order to beg for mercy to become the submissive empire, you have to send a request and ask for a treaty of Protectorate/Subjugation in the "Give" section
For default AI's: If you have six times their score, you can make them a Protectorate; if you have eight times their score, you can Subjugate them; if you have ten times their score and are not allied with them, you can get them to Surrender. This is not absolute because this decision is modified by the other empire's mood toward you.
Unless you have a positive treaty with someone you cannot see what treaties they have in the treaty grid. If you have a positive treaty with someone else who also has a positive treaty with them you can see their treaties "by proxy". (Tesco Samoa)
For treaties of Trade Alliance or higher, your empire will give and receive resources to the allied empire. For Trade Alliances: Minerals, Organics and Radioactives will be shared. For Trade & Research Alliances and Military Alliances: Minerals, Organics, Radioactives and Research will be shared. For Partnerships: Minerals, Organics, Radioactives, Research and Intelligence will be shared. The shared percentages start out at 1% the first turn after the treaty is accepted and increase at 1% per turn up to a maximum of 20%. The shared resources you give to the other empire are not deducted from your production; they are generated in addition to your production so this does not lower your production to your general "pool" of resources. The amount of resources you receive is modified further by the Political Savvy percentage assigned to your empire at the time of empire setup. Example: Assuming you have had a long standing Trade Alliance and are getting 20% of the ally's resources. If you lowered your Political Savvy percentage to 80%, then the amount of a given resource you receive on a turn = (ally amount produced) x (0.2 for the Trade Alliance) x (0.8 for your Political Savvy). If your game setup doesn't let you see the ally's score, you can use this formula to calculate the ally's production: (Ally Production) = (amount received) / [(% amount for the alliance) x (% amount of your Political Savvy)].
| Manual (SEIV)