Jace crouched on the second floor of a building and looked out the broken window. He was staying to the side of the building as he looked over the Holy Empire's base. They had patrols and lookouts outside of their premade metal walls. Inside of the enemy compound he could see the destroyed building that used to be the Holy Palace.
It was not by any measure a shaky piece of hardware. But he was right about the roof being a weak point along with the idea that they would not store the civilians they kidnapped in the Holy Palace. They used that place as an ammunition and weapons depot along with their central base of operations. Unfortunately his barrage did not set off any of their stored ammunition.