The Soviet Union had a buffer zone of 'Warsaw Pact' allies, separating its border from the capitalist world.....
And here we have the growing strength of Nato, which has spread east ...and people wonder why Russia is drawing the line at Ukraine? Come on!
I doubt there was any agreement on that
Russian Occupation Force in East Ukraine distribute fliers to locals instructing them on how to behave.
Including turning in those who are pro-Ukraine.
https://www.youtube.com/watch?v=3T6m3jidE5A&feature=youtu.be
Obviously Russia sees NATO and the west as their enemies, which never changed. Now they have a leader who think eastern Europe is still part of Russia.
Here's a simple response.
Ukraine had no interest in joining NATO.
Russia has invaded Ukraine.
Ukraine now has an interest in joining NATO.