In August 1945 the only two nuclear bombs used in warfare were exploded. Since then there have been many nuclear explosions and many wars and battles, but the two have not combined again. There have been close calls, but so far the world has been fairly lucky.
Who will break the nuclear peace, such as it is? That is, who will fire the *first* nuclear shot?
A terrorist organization
The delivery system will be
a ballistic missile.
a cruise missile.
a manned aircraft.
a drone aircraft
a ship or submarine leaving a bomb in or near a port.
a truck parked and left.
a suicide bomber.
The result will be:
A rapid nuclear escalation to the end of the world.
A rather large, but still limited, nuclear exchange.
A dozen or so nukes will be popped.
A nuke for a nuke, and it will end with 2 or maybe 4.
Just one nuke will be popped.
Just one nuke, and it will be a fizzle (still several tons yeild).
Just one nuke, but it will be very embarrassing complete dud.
Nothing, as nobody will start popping nukes.