The first battle during the Imperial invasion of Rubia between the Royal and Imperial armies was at Kaedwen Crossing.
For weeks before the battle the Royal Army has been fortifying the Rubian side of the Red Orin river, waiting for the inevitable onslaught from imperial forces. The battle started with right after sunset as a large contingent of Crimson Tide tried to ford the river. As the Rubians were prepared for this, the Tide sustained enormous casualties. They were mostly freshly recruited Cleaver orcs.
What the Rubians did not know was that under the cover of darkness (and with magical help from the Directorium) the elite Imperial Legion crossed the river and managed to sneak up behind the Royal Army. Just as the wave of veteran Tide soldiers started attacking from the front the Legion attacked the Rubians in the back.
From that point on it was no longer a battle but a massacre. It was only the heroic sacrifice of the Knights of the Holy Flame that saved the Royal Army from certain doom. The knights held the Legion at bay while the rest fled to the Willow Grove. The Imperial Army did not dare to follow fearing the power the local druids had over the swamp.