Everything. Am not talking about the Geneva Convention but includes the undocumented moral arguments, pre and post WW II, from all sides. If anyone has precedents, it is US. We firebombed JPN and Germany, remember? But we did not employed the same in Iraq and Afghanistan. We developed more precise munition, true that it is less out of those moral concerns and more out of tactical needs, but the outcome is still the same -- less civilian casualties.
Before our squadron deployed to Desert Storm, we had a briefing where our ROE were three main items:
- Aircrew recovery
- Airframe recovery
- Target destruction
Basically, if any sortie is uncertain when over the target, RTB fully armed if necessary. The rules were not absolute for all situations but at least they gave us what we called 'partly cloudy' guidance rather than full haze and fog as so often happened in previous generations of air strikes. Am using weather terms metaphorically here.
Avoidance of civilian casualties -- as much as tactically feasible -- is now embedded in Western armed forces. Russia do not have to be signatory to our agreements regarding conducts in warfare but that does not exclude Russia from criticism and even legal prosecution if necessary.