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Given the following post, respond as if you're commenting on Reddit:
human
[Last Airbender] How would everything play out if the Day of the Black Sun Invasion succeed?

Despite Azula's warning the eclipse invasion goes as planned for the most part, Aang encounters a powerless Firelord Ozai, but refuses to kill him but still knows he can't escape so Aang insteads uses his bending and captures the Firelord then brings him back to camp.

What happens now?
gpt
Viva la Fire nation resistance.

Azula and some fire bender soldiers would start a guerilla warfare against the occupation. 

Earth nation reparations are so high that fire nation citizens are struggling to feed their children. 

After 20 years of uneasy truce, another war erupts, as a fire nation soldier ascends the new-found fire parlament. Aang tries to call for a "peace in our time", but the starved fire nation citizens won't have it.

Since both sides suffered huge losses in the last war, both want revenge and won't forgive the atrocities that were commited.

Basically "the fire nation attackes, 2.0". Now with submarines and missiles and air planes, Korra style. 

Aang's last involvement makes it look bad if he was to intervene again on behalf of the other nations.