Something to consider for the future, assuming vassal behaviour is unchanged in the new version: At the moment, civs become vassals if they lose a city and then have 4 or fewer cities. I have a situation in my game where the Illyrians had 4 cities (though they were master of the Macedonians who had 3 cities) and Athens had 5, one of which was a far-flung city they took from the Dacians. The Illyrians took that city and Athens became their vassal despite being much more advanced. But because they have a cramped starting position they found or take cities a long way away. I don't know if there are other conditions that have to be met not mentioned in the civilopedia, but if not to me it makes no sense for Athens to capitulate in those circumstances. They hold all their original cities, have strong armies and, as I said, are far more advanced. Maybe there should be additional conditions, such as the winning civ has to have x more cities or the loser doesn't offer to become a vassal if the lost city is a certain distance from the capital. Losing a remote outpost shouldn't cause capitulation if a civ has a certain strength IMHO.