Indiscriminate attacks on non-combatants civilians is a war crime under the Geneva Convention.

As for WW2; the Nazis bombed civilians in London for some time -- what did they expect would happen? Neither act was allowed under the rules of warfare ...

For reason of the major actors involvement in Syria; Iran, China, and Russia, it will probably be up to the Syrians to work this one out for themselves.

The Russians have long been Syria's major military suppliers so the use of Russian war machines in this civil conflict is not surprising at all.