what triggers appearance of barbarians ? in my game it was all going well, about 8 cities, ahead or thereabouts in most things, and then two other nations declared war on me. since i was ahead on most things, they weren't too hard to knock down a peg. one only had 3 cities so i took 2, the other around 5 and i took 4. both every single turn tried to make peace but they always wanted me to give back one of the cities id taken plus a bit of cash so i kept refusing. weirdly this meant the whole world thought of me as a warmonger, even though it wasnt me who'd declared war.
anyway i was down to one city each of the 2 nations when i noticed i didnt have any money, was at 0 and losing every turn. tried to rectify this by manual placement and stuff. and then it let go some of my army, and all of a sudden there was dozens of barbarians all over the shot, i mean over a dozen barb troops all over the place all of the same advancement of my best troops.
so was this just random? or because of my negative treasury? or because the treasury issue meant my army disappeared? or because of unhappiness of the other countries?
just wondering so i can avoid it in future, now ive spent about an hour of turns just trying to battle barbarians and not thinking about anything else. feels more call of duty than civ.