[G.K Zhukov]

"property involved in combat" is not the same as your "provided that the enemy is using said infrastructure for the purposes of war".

Clark said something along these lines after a week of bombing Serbia, on a press conferanse that was relayed on norwegian tv (prob also on bbc, cnn and most other networks):
We are out of military targets, so we will widen our target list. I remember it quite well, as I as puzzled by how openly he said it.
And the next thing you know, civilian targets and infrastructure got bombed.

It's not suprising that US resorted to terrorbombing to force a surrender, they did exactly the same against North-Vietnam for instance.