I think that if Ul'dah was smart it would just pick away at anyone who entered the desert, and avoid a large battle until it was favorable. At the same time they'd just pay mercenaries to attack the enemy at home. I think Grid would fight as a medieval army, Limsa would fight more like a professorial army (similar to the british during colonial times), but I think ul'dah would fight more as a renaissance/30 years war type army.
Aka, they would have a large army, but it probably wouldn't get used for much besides sieges. Instead they'd use large scale pillaging and looting tactics with mercenaries to attack the other cities territories at home. It's easy to stop an army, but it's hard to stop hundreds of small bands of essential bandits who will just steal and kill.
Either way though I don't think any city state could really win. You completely underestimate how long cities can hold out in a siege. Ul'dah could probably hold for months if not years, as many cities often did. It does had some internal water sources, and they'd probably expel all the refugees first thing.
Edit: For example, Vienna was sieged by the ottomans in 1683, and easily held out for two months before reinforcements arrived. At the time the city had around 150,000 people.
Aka, they would have a large army, but it probably wouldn't get used for much besides sieges. Instead they'd use large scale pillaging and looting tactics with mercenaries to attack the other cities territories at home. It's easy to stop an army, but it's hard to stop hundreds of small bands of essential bandits who will just steal and kill.
Either way though I don't think any city state could really win. You completely underestimate how long cities can hold out in a siege. Ul'dah could probably hold for months if not years, as many cities often did. It does had some internal water sources, and they'd probably expel all the refugees first thing.
Edit: For example, Vienna was sieged by the ottomans in 1683, and easily held out for two months before reinforcements arrived. At the time the city had around 150,000 people.
