Losing even a hundred of them in this war was an acceptable loss for him. In fact Arthur put a higher number for the total casualties in this war; one thousand cities.
If he managed to get out of this war with less than that number, then he would consider himself lucky. So in his eyes, losing dozens of cities early on in this war wasn't something worthy of his attention, rather his panic.
More devastation was destined to happen, especially when he had the impression that this wasn't the total power of his enemies.
This was just the opening move of this war.
'Don't move everyone,' he warned, 'I believe more portals will open after you deploy the armies.'
