Sherekan city was not a small one, as it had lots of guards and powerful people that lived there. You could say that it had the strongest people in all the Shukar Empire.
That was enough to fend against most invasions, and that was the reason the nearby empires and kingdoms did not attack it until that point, having the last known battle 60 years ago.
The Emperor was scared that someone would try to attack them, as the Shukar Empire was getting weaker and weaker as the years passed. A trace of that was the economy, who was completely broken.
Now, humans may have reasons to attack the empire, but monsters? No one knew where did that wave of monsters came from, or what was the reason for them to be there.
Was someone behind it? Or Sherekan city was just unlucky and impeded a monster migration?
These were the questions everyone wanted to know the answer to, and Arthur was one of those people.