In much contrast to Cambyses's wish for the enemy to waste time continuing to destroy something that was of significantly less value to her, as soon as she had thought such, much to her horror she began to notice a large number of torches appear from underneath the overgrowth, moving away from the iron mines, and slowly headed up, straight towards her
'The enemy has started moving!' Cambyses immediately understood.
But soon noticed that the mass of torches inexplicably had decided to divide itself, and then suddenly one of the groups diverted its course to head in the opposite direction, which was where the cement crushing plant was situated.
Yes, the lights that Perseus noticed were from that place, which ran 24/7 to crush the cement clinkers.
And seeing Perseus divert part of his army to attack there, for a while Cambyses was a bit confused.