I believe it's the extra cost for when a unit is out of your territory.
E.g. You build a warrior. He has an upkeep of 1, before inflation. You move him into neutral territory, he now costs 1 in upkeep and 1 in supply, for a total of 2.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.