Throwing the rear of the Burgundian army into chaos wasn't particularly difficult, given how poorly armed they were compared to the duchy army. If you strike at an effective moment, weighing the enemy's morale and combat power together, you can break them down with ease. Of course, this is me boasting. Not just anyone can pull it off.
As the Burgundian army collapsed, the duchy army began pressing forward.
The Burgundian cavalry's numbers had dwindled considerably, and when the main force fled, they ran as well. The Beren lancers, reduced from ten to five, chose to attack the fleeing Burgundian infantry from behind rather than chase the retreating cavalry—routed infantry were easy prey and guaranteed achievements.
Easy prey indeed.
