The source you provided makes clear that sieges are lawful provided non-combatants aren't affected (so starving civilians, barring humanitarian aid, etc. makes a siege unlawful). Furthermore, it states that sieges where non-combatants are affected were lawful prior to the 20th century.

In the context of ATLA, there's not really enough known about the geopolitics of the world to properly gauge whether or not besieging a city is a war crime. The frequency of sieges in the show (North Pole, Ba Sing Se) can't be used as an argument for their legality since they're undertaken by a state that is known for mistreating prisoners of war, disrespecting geopolitical boundaries, and so on. Regardless, you can't judge the Avatar universe by real world law.

[–] pandapoo@sh.itjust.works -1 points 5 days ago

If they were laying siege to a military base, sure.

But they were laying siege to a city.... Maybe you should go read up on the history of siege warfare to get a better understanding of how that impacts civilian populations. Heck, forget medieval times, just look back to the '90s to the Siege of Sarajevo.

Also, prior to this 20th century, there were no Geneva Conventions, and prior to Nuremberg, no international war crime tribunals. So not sure what your point is.

Either way, it's a cartoon world. My entire point was that cartoons shouldn't be held to a standard that must reflect our reality, but that logic must applied equally. Either it reflects our reality, or it doesn't.

You can't say it reflects our reality, but because he was a good guy in the end, that negates his war crimes. That's not how war crimes work.

So, if we're discussing this in terms where the cartoon parallels our reality, then yes, laying siege to a city full of civilians is a war crime, full stop.