Ok, i am very far into my game of civ v atm, i have many allies. The problem is with the Byzantinum Empire. It seesms that any city state connected to their borders gains some sort of static influence toward them Byzantium is completly bankrupt and in negative GPT yet every so often they will supplant me as city state ally. In that occasion i will buy back influence.(I have a strong economy) I would just like to understand why this is happenning, if there is some sort of policy or tenent, or something that is specific with the byzantium empire.
It can be a result of gunboat diplomacy, but there are other factors that also play a role here, such as:
if these city-states share the same religion with Byzantium, their influence decay will be slowed down by 25%;
if Byzantium has patronage opener, influence decay will also be slowed down by 25%.
If Byzantium has these factors but you don't, then their influence decays slower than yours, so effectively their influence is gaining every turn relative to yours.