I remember that. That was one of those freak battles. IIRC, you didn't even know they were there and weren't expecting a battle? His death was a bit of a turning point in the invasion for a couple realms, I think.
He spotted them, but simply paid little attention to them, considering how small the unit was.
Those events did forge BT's history afterwards.
Nicolas later returned, started with a blank slate, but JO's old friends took him under their wing while the republicans alienated him. So he followed in JO's footsteps. But Mordred had had enough time to prepare, and Nicolas' preventive rebellion came in as too little and too late to cast him out. Which sent him to Enweil, where he spread his militaristic agenda and pushed the continent's superpower out of its slumber and into an agressive campaign, coordinating with Louis-Joseph who orchestrated the emergence of wars continent-wide.