That is why I consider a Russian ICBM (non-nuke) launched at the countryside outside of London, England (so Little Linda is safe) as a “sky” or “scare” event.
Warsaw is also a possibility.
It may, or may not, reach its target; the launch and vector are the event.
This will cause Biden to attempt to act as C-in-C.
Putin knows.
Caveat: the real impetus is more likely NATO troops on the ground in UKR, engaged in fighting.