Innocent population or not.

Peace be upon the Grand Master Shlita.
Terrorism’s devious methods are well known in that it uses civilians as human shields. Some argue that to defeat terrorism, civilians must be killed in aerial bombings and the like, not only because this will save the lives of soldiers, but because the population supports terrorism, encourages it, and takes pride in it. This is true of terrorism. What about the army of an enemy country that has facilities in cities? Is the population also guilty of supporting its army? Logic dictates that it is legitimate, or is it similar to the World War to bomb entire cities with their inhabitants?