Yes.
All these years of mutual assured destruction have not erased the terrible possibility that two egotistical world leaders will posture, escalate and bluff and escalate some more until only World War III is left with nukes to wipe us all out.
We can't stop them from starting a nuke war any more than in the 1964 Dr.Strangelove. Why can't those screenplays stay fiction?
“We can’t stop them from starting a nuke war any more than in the 1964 Dr.Strangelove.”
—
And if you’re not worried about the leaders, there’s always the underlings and accidents to keep in mind!
https://en.wikipedia.org/wiki/List_of_nuclear_close_calls