Explanation: On the frontiers during the Empire, Roman soldiers were regularly taken out on punitive expeditions against 'barbarian' polities. This served multiple purposes:
First, it served as a deterrent. Loot what you can, burn and drive off what you can't. By reminding enemy forces of Rome's ability to strike back at them, it discouraged similar enemy raids seeking to loot and enslave Romans.
Second, it served as a diplomatic tool, in a strange way - the threat of Roman raids incentivized 'barbarian' polities to become 'friends of Rome', pledging not to undertake hostile action or support hostile actions against Rome - which would exempt them from being the target of such punitive expeditions.
Third, the professional soldiers of the Roman Legions and Auxiliaries often joined up with an expectation of at least some enrichment beyond their regular pay - after a period of calm, some plundering could go a long way towards defusing tension amongst the bored and frustrated soldiery.
Distinction between combatant and noncombatant was rarely, if ever, made, and the Romans regarded such raids as in accordance with international/natural law (ius gentium). If you are not at peace with a polity, everything is fair game - and if you are at peace with a polity but the people are not adhering to the terms the polity agreed to, everyone in the disobedient regions are 'bandits', and deserve whatever they get coming to them.
The past is a cruel place, and the Romans were no strangers to cruelty.