I would think the invaders would take the city and hold it. I've been to a Mall just outside of Dubai just dedicated to gold and jewellery. That mall alone probably had more wealth than many smaller cities in the world. So there's plenty to loot.
This reminded me:
Siege of Tyre 332 BC - Alexander the Great
https://www.youtube.com/watch?v=98inDANKtEs&t=290s