Just finished my first ever game of BNW
Played as Shaka and got a
victory.
I wiped out all other civilizations on my continent, but never attacked a City State. I'd like to think they responded well to that but in all honest I can't pin down why 4 City States on my continent were my allies NON STOP for 2000 years.
I settled down and down sized my army to save gold (for bribes) after I saw this and got my first taste of the world congress. The only other civs left in the game were the Swedes and the Indonesians. Because we had no contested borders we were best buddies till the modern era until we each picked different Ideologies.
For reasons I can't fathom, I decided to go with Autocracy even though I'd long since decided I wasn't going to try a Conquest victory.
I just hunkered down, got to the stage where I was at +1000 science, +500 gold and +70 happiness per turn.
When it came to my turn in the congress I gave myself some leg ups. I managed to convince the Indonesians to partly vote in support for Autocracy as world Ideology, then Sikhism as world Religion. From there I had a good base of delegates not counting all my city state allies. I ended up with a massive gold reserve at the end as literally threw 3000 gold at a city state in the turn before the election to get the allied status.
In the mini fiction of that world I imagine there was some serious unfinished business and bad blood after a serial-conqueror somehow led the world to peace.