Eight years before the start of the Ys series, the Romun Empire invaded the Kingdom of Gllia in order to annex it into the ever-growing empire. Imperial forces dominated the war from the beginning until the end. Following a large-scale battle on the outskirts of Balduq, the Gllian army fled before the eyes of the Romuns into the city of Balduq.
Before long, the troops stationed in Balduq could not overlook the continuous detoriation of the city's public order and ration reserves and collaborated with local militia to lauch surprise attacks, but the cowering general leading the local militia changed his mind and ceased his support, which lead to a crushing defeat of the stationed troops. The royal castle immediately surrended to the invading imperial forces. In the rashness of the Romun army for seek fame, it was publicly announced that the castle was capitulated bloodlessly. The war ended with victory for the Romun Empire.
The war left the Kingdom of Gllia in ruins and it was subsequently annexed into the Romun Empire as a province. The royal family fell, with the king dying in battle. His only daughter, Princess Eleonore, went missing.