I think it's paramount to first consider Russian perceptions and how their history still dictates current thinking -- the threat of domination from western powers.

Where are these ‘allies’ that they boast are now under their first strike nuclear umbrella? Serbia or better yet the break away Kosovo? NATO is probably being viewed as taking land that Russia had for years and now their (strong arm tactics) influence in the region is dwindling. Even if Serbia was a self-declared Russian ally, how would Russia otherwise support them with NATO nations between the two?

Georgia and The Ukraine threaten Russia’s southern flank with NATO membership and even further isolation. The Baltic States are literally a thorn in their side, and the USA wants to plant missile defense batteries in Poland (to defend exactly who?). We'll need a rocket scientist for that one

Following General Yury Baluyevsky's comments about the use of nuclear weapons are two significant comments from:

Retired General Vladimir Dvorkin, formerly a top arms control expert with the Defense Ministry, said he saw "nothing new" in Baluyevsky's statement. "He was restating the doctrine in his own words…"

Moscow-based military analyst Alexander Golts said that when Russia broke with stated Soviet-era policy in the 2000 doctrine and declared it could use nuclear weapons first against an aggressor, it reflected the decline of Russia's conventional forces in the decade following the 1991 Soviet collapse.

"Baluyevsky's statement means that, as before, we cannot count on our conventional forces to counter aggression," Golts said on Ekho Moskvy radio. "It means that, as before, the main factor in containing aggression against Russia is nuclear weapons."
Obviously the Russians don’t understand…whom, given the choice of the current regime or NATO wouldn’t go west?

We’ve been smokin' along (and over them) since the early 90’s and, IMO they agreed because they had no other choice. Well, those days (for now) are gone.