Rereading Bayou, you realize Ouki could've given Riboku an L by abandoning Moubu and Ryuukoku (since Ouki wouldn't have been killed), and simply retreating back into a defensive formation. But pushed forward because he wanted to save Moubu and Ryuukoku:
You realize that Ouki's strategy perfectly countered Riboku's overall plan. And it took Moubu ignoring Ouki's orders, where he didn't want Moubu to step out of that range even if Houken had appeared, for Riboku to actually lead him into that trap. And Moubu ignoring orders was neither predicted or taken into account by Riboku.
This smart guy Moubu not only left the range, but proceeded to fall for an obvious plan, that effectively fucked him up as well + destroyed a 25k army, that Ouki could've strategically used to counter Riboku, to the point only a 1000 man unit that could "barely lift up their weapons". This then forces Ouki to go completely blind on the battlefield since he loses all contact with the HQ, due to needing to save Moubu and Ryuukoku. And then Ryuukoku blatantly notices that Ouki was doing warfare that not like him.
Sad as fuck, we never even saw Ouki being able to utilize his own warfare to it's peak from start to finish. And if you're asking me, long as Moubu doesn't step out of the range and effectively follows Ouki's orders... Qin ain't losing that war.
Which is why nobody reassures Moubu that things would've happened regardless, unlike when Mouten reassures Shin that Riboku would've escaped regardless of whether the HSU got paralyzed or not. Ouki or anyone else later doesn't take the burden of blame off of Moubu. And to Moubu's credit this was the first big moment of growth for him, since he proceeds to admit it was all his fault.
@SakazOuki There you go, more Riboku dehype. Without Moubu's fuck up, Ouki easily could've won, tied it or changed up the entire war scenario by pulling a strategical retreat into a different place or lord knows what. Saying Riboku beat Ouki based on ability is just a disingenuous take.