Please correct me if I'm wrong here, pulling it outta me ole' arse but I read this somewhere. Ukraine gave up those nuke's and the other side of the provision prevented NATO from expanding their eastward expansion. Since Ukraine relinquished their nukes, as part of that agreement, NATO has expanded it's eastern expansion with the inclusion of maybe 8 extra countries. Some of them even contiguous to Russia.

Not trying to spead disinformation if incorrect, but I don't care enough to GoogleFu it.

But if true, or partially true, I could see where Russia is pizzed. Doesn't warrant invasion by Russia of Ukraine from a Westerners viewpoint, but then again, they have a different perspective.

Cuban missile crisis anybody?