Expectations of war

What is this idea floating around that there is such a thing as a war where only the combatants get hurt, and, if any others do, somebody's not following the rules? this does not make any sense whatsoever, not by common sense, not by the history of war, not by any commander of any army, or any wartime leader.

where did this notion come from? all the new precition munitions made nowadays? that makes for some more control, but cirtainly cannot garantee that NO civilians will feel the effects.

I don't get the idea.

Never, never, never believe any war will be smooth and easy, or that anyone who embarks on the strange voyage can measure the tides and hurricanes he will encounter. The statesman who yields to war fever must realize that once the signal is given, he is no longer the master of policy but the slave of unforeseeable and uncontrollable events.
Sir Winston Churchill