Poison
In the next few days, Sébastien ensures that they surrounded Pontus. They did not attack the kingdom but whoever stepped out of the gates never returned.
Pontus was close to the sea, it had a low wall facing the sea, this was the only place that was not guided. The message was clear, they were forcing the people from the north to retreat. Of course, Pontus did not want to initiate an attack like this. Since whey were already surrounded and they came with a lot of Archer. It was clear that once the war started, even if they managed to defeat the people outside will destroy the kingdom.
Moreover, Pontus could not house all the men from the north. The tenths had to be raised but the weather was too cold. After traveling in the water and ending up in this kind of condition no matter how fit the men were they began to fall sick.
Of course, this was what they thought happ9, none of them were aware of the fact that their water has been poisoned.