If a player has captured a City State what is the defensive value if it is attacked? Does it retain the City State defensive value of 8 or is it simply regarded as a player city so gets a defence value of two times the terrain - which a City States are always situated on grassland will be 2?

Thanks.

If you conquer a city-state you replace it with one of your cities, I'd say then the normal rules that apply to any of your cities will affect this one (so no 8 defence value).