I am sorry that you are not imaginative. But war is not about niceties. The US, from a position of absolute strength and domination, merely pretends that it is. And for that strength we have spared many civilian lives that would otherwise be lost if we needed to carpet bomb things. But on any occasion where two belligerents are not massively mismatched, anything goes. Any thing. And you have to imagine getting a dirty bomb into Moscow, or generally F'ing Russia up would be a primary goal of their opponent.
Pain for pain's sake, to make the opponent think twice.
Regarding how wars are actually conducted, look no further than the bombed out husks of cities in the middle east. Russia conducted much of that bombardment just in the past decade. We also were not so nice against ISIS, did you see pictures of Mosul after it was retaken? Point is... anything goes. You simply fail to imagine what that could look like.