In a recent game one of the AIs went to war with a couple of my friendly/allied city states. But I didnt want to go to war with that AI.
I was able to easily defend the city state by getting a couple units there first and merely making a wall with them in front of the city state. The AI melee units couldnt easily attack the city, they had to go around me, suffering fire from the city state each turn, and then when they got to the back of the city to attack it they were weak.
A couple of my units guarding the front side of a city state was enough to enable the city state to defend itself from attacks of 6-7 units, and the city state had a mere 1 unit for itself, garrisoned in the city.
I was able to easily defend the city state by getting a couple units there first and merely making a wall with them in front of the city state. The AI melee units couldnt easily attack the city, they had to go around me, suffering fire from the city state each turn, and then when they got to the back of the city to attack it they were weak.
A couple of my units guarding the front side of a city state was enough to enable the city state to defend itself from attacks of 6-7 units, and the city state had a mere 1 unit for itself, garrisoned in the city.