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.
The worms were ordered to dig, much deeper than what they usually do and then towards the town before turning upwards after they bypassed the walls. The worms did what they were ordered to do so and everything worked in their favour.
The humans failed to find out about those worms digging under their feet.
Though the process was long and it took a long time to do so. They were successful in their endeavour and were able to dig tunnels from the rear of the monster tide directly into the heart of the town where the support personnel were located.
Now the pathways are created, it's time for them to act and do what they came here for, to destroy the town.
---
The command was alerted once the roars of the monsters and the cries of humans came from the town. They understood that the monsters were able to breach through the defences and reached the heart of the town.
From there the rear of the defence is in danger.
The support personnel can do nothing to those monsters. Even the ones who went there to rest or to get healed may not be able to stop those monsters.
Those monsters dug tunnels into the town directly bypassing the defences. Now that they are vulnerable in both directions and are doomed to fall.
To avoid that catastrophe, now they truly need reinforcements, no matter what.
Without the reinforcements to sweep away the monsters, Repest is certain to fall.
---
"I need a few spellcasters and a few warriors to follow me into the town", the commander shouted out loud.
Everyone knew what was going on, once they heard the roars and cries. Monsters somehow entered the town and their backs are now vulnerable.
They now have to fight on two sides and that would not end in their favour no matter what.
Even though that was the case, they had no choice but to fight with all their strength now. Even the ones who had thoughts of deserting the frontline now may not have a choice of escaping the fight.
There might be some chances of escaping while fighting but those chances would be very low.
Once the commander gave the order, a few spell casters moved from the wall to deal with the pests that entered the town. Once they clear these pests, they can return to the front line where it would be much safer for the spell casters.
Unlike the spell casters whose lives were at stake and who had easy access to the town, the warriors who were on the ground fighting couldn't return to the town, without leaving gaps in the defence but it was something that couldn't be avoided.
So a few followed the commander into the town.