Worth reading:Civilian casualties, leaks and the ancient view
By and large, Greek and Roman military command had it relatively easy
when it came to leaks, civilian casualties and the PR side of warfare.
To put it at its crudest, the imperial Roman legions would go off to
conquer some bit of foreign territory, they would do it any way they
could and come back home and boast about it. Not many people in Rome
knew or cared about war crimes. It was winning that mattered.
Of course, it looked different from the barbarian point of view, but the barbarians got very little chance to put their point of view at Rome.
But even in the ancient world, it wasn't quite so simple.