They didn't take much time to turn the entire ground into a wasted land. All kinds of breaths were used here, and in the end every single trap in front of the passage was destroyed.
As for the walls they didn't take long to be destroyed, then Henry led the group and dived deeply inside the enemy forces.
"Follow me," Arthur shouted while turning around, "let's clear all the enemies and create a path for others."
He knew he couldn't kill everyone in the short time left for him. Leaving the reinforcements also in the open wasn't an option, as the entire army at the ground was able to kill hundreds of thousands in a short span of time.
He didn't know if the incoming reinforcements had any mages inside or not, and he couldn't tell if they would be depended upon.
So he decided to take the worst option; they were useless and he had to act this way.