ironically, the irbm launch with prior warning is an attempt at de-escalation. the way this works is that you retaliate in a way that demonstrates your willingness to escalate without putting your opponent into a corner that forces them to retaliate in a way that forces you to escalate even further. at the same time, you are trying to show that you will ultimately have the option to take that very final escalatory step where your opponent no longer has options that don't end in mad. russia does not believe it will ever need to nuke nato territory before the west is out of realistic non-mad actions. nuking ukraine, somewhere in a low density area however is something putin has demonstrated he is willing to do. the point of the irbm is a message to western and ukraine public. to western audiences it's "our nukes aren't in shambles so mad is still a thing"; to ukraine it's "the west knew we would lob an irbm, closed their embassies and won't retaliate or have an answer for it and won't save you or respond in kind if/when we nuke you."
United States