The fall of Repest has begun (2)

The victory of the monsters is all but assured as long as the magic users are dead. To make sure that happened, they silently sent their underground monsters to dig tunnels under them and kept quiet about that by making all defenders concentrate on them, making them forget about what was happening underground.

The high-rank monsters are not dumb and they know that humans are very clever. They should be watching out for any surprise attacks, especially from underground.

Even monsters have skills that can detect movements underground. There was no reason to not believe that humans don't possess such skills. It was most likely that they do have such a skill and that too in more than one.

So the monsters were very careful when they executed their plan of infiltrating the town using the underground as a means.