Alliances, pacts, spheres & vassals
Diplomacy offers a full ladder of bonds — from light non-aggression pacts up through full alliances, spheres of influence, tributary vassals, and unified federations — each with its own thresholds and costs.
How it works
The lightest tools are pacts: a non-aggression pact (nap) and a defensive pact (def). Full alliances require relations of at least 50 (ALLY_REL), and AI powers offer them through their persona ally weight when relations clear a comfortable floor. Economic ties are a parallel ladder needing relations of 10 / 40 / 70 for tiers 1 / 2 / 3.
Below alliance sits subjugation. A tributary pays a slice of its GDP each tick and suffers stability drain, scaled by subtype: a vassal pays 3% with no drain, a protectorate 6% (drain 0.15, cedes its foreign policy), a constituent region 5%, and a colony a punishing 12% (drain 0.5). Each subtype demands a minimum war level to impose and carries a per-tick rebellion chance, from a quiet 0.25% for protectorates up to 1.2% for colonies.
At the top are voluntary unions. A personal union needs relations of 60 and only works on a partner up to 1.4× your power, with a tiny 0.15% per-tick secession risk; a federation demands relations of 75, a partner no stronger than 0.85× you, a 3% funding contribution, and a higher 0.5% secession risk. Spheres of influence sit between alliance and subjugation — real influence, but a looser leash than a tributary.
Formulas
relations ≥ 50 (ALLY_REL) to form a full alliancerelations ≥ 10 / 40 / 70 for econ level 1 / 2 / 3vassal 3% · protectorate 6% · region 5% · colony 12% of GDP per tickpersonal union: rel ≥ 60, partner ≤ 1.4× power · federation: rel ≥ 75, partner ≤ 0.85× powerKey numbers
How to play
- ▸You need relations of 50 for an alliance but only 10 to open trade — use economic ties as the on-ramp that lifts relations toward the alliance threshold.
- ▸Colonies are lucrative (12% of GDP) but the 0.5 stability drain and 1.2% rebellion chance make them the least stable of subjects — protectorates are the safer squeeze.
- ▸Federations bind stronger than personal unions but demand a weaker partner (≤ 0.85×) and relations of 75; groom the relationship long before you propose.