|Battle of Opethburg|
|Grand Alliance||Yamato Empire|
| Kagetsu II|
The Battle of Opethburg took place in and around the town of Opethburg in Remon in 1003 AE. It was the second large-scale battle in which the entire Grand Alliance participated in. Despite losing men, the Alliance eventually captured the city from Yamatian forces and thus got its hands on a never-ending bow supply which the Alliance's archers put to good use in later battles.
- Main article: Battle of Folsworth Woods
The Battle of Folsworth Woods had ended, and the Alliance had been victorious albeit with a heavy cost. Knowing that the fleeing Yamatians would soon rally a new force behind them, Marcus Sarillius and Kagetsu II decided to act and move northward to intercept the Yamatian supply route which went through the lumber town of Opethburg. Despite the soldiers being tired, they followed their leaders north and prepared for one more push which would determine whether their victory at Folsworth Woods had been a fluke or not.
The battle was short and fierce. The Alliance managed to attack before the Yamatians had prepared for themselves, and the Myrdosin elves with their pegasi horses proved to be effective in slaying Yamatians. After just a few hours of fighting, the remaining Yamatians either fled or surrendered, and the Alliance marched into the city.
- Main article: First Battle of Remonton
With Opethburg's fall the Grand Alliance was now in control of one of the important supply routes in Remon and had access to a large stock of wood from which to make arrows and bows. They had shown the Yamatians that they were a force to be reckoned with, and thus the Great War had begun in full force. Realizing that they could use the chaos within the Yamatians' ranks as an opportunity, Marcus and Kagetsu II wasted no time and began preparations to march directly to Remonton where the Council of Regents resided.