Military action
The remains of the countries fight over available resources.
Since both countries are in tatters after the end of the Dark War, the scramble for resources and ways to survive ended up taking a toll on the people and soldiers. The countries, not knowing who to blame for the immense war that almost destroyed the world, blamed each other and ended up creating another smaller war that only some of the people really partook in. The collapse of Pranio was imminent, and with Lisea's 'victory', it was left the one standing. However, due to a collapsed government without a ruling figure, it too fell. Luelle was founded soon after, circling the sacrifices of the Valkyries in saving the world.