Around half an hour after the demon horde first made contact with the zombie army near the palace gate, the horde also approached the station hall where the Liguritudum army command base was located.
Since they already knew the demon horde was coming, they were prepared. The soldiers set up layers of barricade along the tunnel that was the entrance to the station hall.
This was what Jack had been waiting for. He had been keeping an eye on Linda using his incorporeal state, making sure that she didn't move away.