Yes. And Sozin starts by attacking on the day of a comet coming, when the Fire nation is at its strongest, and they wipe out the air nomads, all of them, except for Aang. Avatar Roku couldn't stop him because he was dead, and so the war started after what became known as Sozin's comet: when the Fire Nation military slowly started to take over parts of the world. They whittle down the Southern Water Tribe to scattered villages, and are slowly starting to take over the world.

When Aang, the Avatar and last Airbender returns, that's when we start to fight back. Me and my brother join him in his quest to restore peace to our world and defeat the Firelord, the latest in line to try and topple our world.