Ala Mhigo had a bad relationship with the other city states. There are no specifics, but it is said that they tried to invade the others a few times.
There was apparently one attempt to recover the city from the Garleans by the local resistance, but it failed miserably. Those that fled the city are scatered between the Black Shroud (in Quarrymill, I think) and a town to the south of Ul'dah, Little Ala Mhigo (which is really a big cave).
There's a lot of information about Ala Mhigo's fall in this thread..
The spoilers you want are the ones about the Fists of Rhalgr and the Last King of Ala Mhigo. The others are interesting lore but aren't related to the city state.
There was apparently one attempt to recover the city from the Garleans by the local resistance, but it failed miserably. Those that fled the city are scatered between the Black Shroud (in Quarrymill, I think) and a town to the south of Ul'dah, Little Ala Mhigo (which is really a big cave).
There's a lot of information about Ala Mhigo's fall in this thread..
The spoilers you want are the ones about the Fists of Rhalgr and the Last King of Ala Mhigo. The others are interesting lore but aren't related to the city state.