[quote=So Boerd]
France and UK have no incentive to nuke every Russian city. Doing so means Russia nukes every one of their cities. They have every reason to just nuke an equivalent number of Russians and hope Russia calls it quits there.
[/quote]

Russia nukes the UK and France. France and the UK nuke Russia back. Even if they don't unleash their entire arsenal, one can assume that France and UK would bitterly target the capital of Russia and one of its major industrial centres.

[b]Regardless of whether they unleash their entire arsenal:[/b] Russia, the UK, and France are all massively weakened via the losses of their capitals and the ludicrous infrastructure damage the nukes caused, not counting the fallout that will follow in the local area. All this does is make other rivals (friendly or hostile, such as the USA and China) stronger. Even if [b]Russia Succeeds[/b], they still end up getting hit with retaliatory strikes, they still lose on the world stage.

That's really how it works.