Why did Fire Nation want to conquer everything again?
Souzen just says something about like:>muh, we have so much prosperity, we should share it with rest of the world by genociding them
I mean historical conquers had actually motivation behind the conquest:
e.g. 19th century Japan's economy relied on the military so they needed it
Genghis Khan and many other nomads just wanted enrich their people
people like Caesar conquest of Gaul was both economic and egoist shit
many autocratic emperors used war to to dislay their authority and divert the attention of scheming nobility
But none of those seem to be the case with Fire Nation