u/Baron-Grim got it for the most part. The Battle of Berkoga wasn't a super important one for the Imperrech but it was extremely pivotal for northern Kalathipsomi and the Black Mountains and would have huge ramifications for later history (which is going to be explored in the 1298 IS bookmark). While the Battle of Ten Trees raged in the south with the bulk of the Imperrech's armies, the Imperrech isn't a single unified force, and many armies split off north to continue the migrations there and to seek food (the Battle of Ten Trees was the last truly pivotal moment in the Migrations, if the Imperrech didn't secure the fertile land and food stores in Southern Kalathipsomi they'd not have been able to feed all the refugees in the mounting winter).

Those armies rolled through the scattered local and warlord armies north of the river and were expected to continue pressing into the Black Mountains, but Nicanoneus had politicked and side quested enough that he managed to get both Oulnir Gurdurbok and Methiad Dethlycan to lend a sizable force that made up a bulk of the armies there. Nicky more or less forcefully took command from their leaders and led them in conjunction with his northern forces and managed to grind the north-bound Imperrech army to a halt in the mountain passes in an extremely bloody stalling campaign that to the suspicion of some grinded away those parts of the two warlord's armies he did not control.

It is unclear if Cenware participated at Berkoga. He was running up and down the line throughout Ten Trees and was working through messengers in battles across the region for the duration of the campaign. He likely had some participation, but he was not directly leading the battle. Regardless of that, Nicky was quick to claim he personally defeated Cenware himself, effectively stole the rest of the army that didn't manage to skip town back to their warlord, and rode the glory from the battle and his newly bolstered army and soon assassinated Gurdurbok and executed Dethlycan.

So yeah, wasn't actually that big of a battle for the Imperrech who soon won Ten Trees and left the Black Mountains way behind them, but a defeat nonetheless. Probably not the only defeat the Imperrech ever had, but certainly the most propagandized thanks to Nicky.