Captured women and children

[Sardaukar]

Also, weren't the atrocities normally indulged in as a lesson? I've read in several sources that populations were spared when a town or city surrendered before the (battering) ram touched the wall, or when an enemy commander surrendered at an envoy's urging.

There seemed to be fair amount of such incidents. I think it was customary that when assault on city started (after negotiations broke, "ram has touched the wall" as in Jerusalem), defenders ceased to have much say on their fate. It depended then entirely of enemy's mercy or lack of it.

Anf there were many cases like Cenabum (where they had massacred Roman traders etc.), Cenabum was burnt by Caesar, the men put to the sword and women and children sold as slaves, because they were made an example and/or punished for their past deeds.

It seemed to be very dishonourable to "cheat" in surrender deals as Roman commander (like doing abovementioned if enemy surrendered without resistance). And most Roman noblemen commanding armies were quite particular with their dignitas and general public image.