All WMD do and in fact any damage to civvies (population) does this. It's not special for WMDs = they just do so much it's immediately noticeable.
But if you decide to steamroll cities with artillery or flatten them with bombers you will experience the same thing.
Essentially it is your decision: Conserve your forces but risk civilian casualties or tread more careful, but risk higher unit losses.
//G
"Going to war without France is like going hunting without an accordion." Gen. Norman Schwarzkopf