From my perspective, Jowy and Riou both are tasked with collecting 107 stars of destiny in order to control Fate. Ultimately, Jowy fails at this and Riou succeeds.
Evidence:
- Leknaat appears to both of them
Bright shield and Sword rune are the same- both carry a true rune
Viktor/Flik=Seed/Culgan
Jowy hires a strategist in Leon Silverberg (often the strategy star in Suiko games)
Characters and others often comment on the glimmer in Riou's eyes (which they say Tir McDohl also possessed). Luca Blight comments on the darkness in Jowy's eyes. (Bright shield/Dark sword)
Ultimately, Jowy is a good guy.
So Jowy joins back with Highland after seeing all the misery that comes of war. He knows City State will lose because he sees how terribly broken their alliance is. He wants to shorten the war so he applies his skills to the winning side. No doubt his burgeoning romance with Jillia (yes I'm aware many of you think she was just a tool for him, I don't agree) and the need to please his parents also influenced his decision.
Then comes Riou, who prolongs the war like heck. From the player's perspective, it seems worth it because now the world is rid of the evil Luca Blight.
However- lets count bodies: Solon Jhee managed to conquer South Window without killing anyone except Lord Granmeyer. He did not sack the city. Kiba and Klaus conquered Radat without killing anyone, apparently. Jowy conquered Greenhill in an embarrassing, yet relatively non-violent way. Matilda basically handed itself over to Highland by assuming it would never be attacked.
In fact, the only places where people were genuinely massacred were the ones where Luca Blight was involved. And Jowy promises Riou and the gang "Luca Blight will not be allowed to have his way with the City State." Presumably this means Jowy has plans to murder him. We also know that Seed and Culgan would likely be willing to join Jowy's revolution/assassination plans. Based on Kiba and Klaus' reaction to the news of Agares' death, its likely they, too, secretly oppose Luca. As does Jillia. Roughly everyone within murder-reach of the Evil-Incarnate opposed the man.
The only place where it is obvious that Riou's efforts definitely saved lives was when Kiba and Klaus came to attack Two River and, despite the treaty, decided to come in and presumably sack the town anyway. It doesn't really make sense for them to do this, so its probably safe to assume they had orders from Luca.
Meanwhile, Riou reconquers Muse, Greenhill, South Window, Radat, Matilda and Highland by force costing thousands upon thousands of lives. In the case of Kiba and Klaus' assault on North Window, Apple said he lost 2/3s of his company of 25,000. That's ~16,700 right there.
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I realize this is getting way too long and I'm going to stop myself. Many of you might look at this and go, who the hell even cares? Well, Suikoden 2, for me at least, is such a hugely valuable story about sacrifice and morality and virtue that diving into its depths is inherently rewarding. Being able to look at this game after 15 times of playing it and still discover something as unsettling as the fact that the Dunan Army (or whatever the canon name is, idk) might not actually be in the right... well that's really something.
My posting it here is probably largely self-serving. A way to make sense of my thoughts as I play through again, but I'm also quite eager to see the opinions other people may have on the matter.
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Side note, I still occasionally work on remaking Suikoden 2 from Jowy's perspective. SoD for Jowy List:
*In many places, the two stories would share SoD's, and it would be a matter of collecting them while there is a small window of opportunity. (ie, recruiting Alex and Hilda right after Solon Jhee conquered South Window)
- Seed/Viktor
Culgan/Flik
Leon Silverberg/Shu
Jillia / Nanami?
Hilda//
Alex//
Pilika/Idk. Nanami maybe?
Emilia//
Clive//
Sasarai (thanks darknight!)/ Luc
Wedding officiator/Gantetsu
Jillia's Maid/Taki
Rowd/idk what Star
Rowd's Sister/ idk what star
Lucia/Star from S3
Kage/Star from S1
Beecham/ idk what Star
Klaus//
Kiba//
Yuber / Pesmerga
Han Cunningham/Shu
Armorer//
Rune shop owner//
Item Shop owner//
Inn operator//
Chef//