And expanding NATO right up to their borders after we promised them we wouldn't, has nothing to do with it?
https://nationalinterest.org/blog/the-buzz/newly-declassifie...
https://nationalinterest.org/blog/the-buzz/newly-declassifie...
The interviewer asked why Gorbachev did not “insist that the promises made to you [Gorbachev]—particularly U.S. Secretary of State James Baker’s promise that NATO would not expand into the East—be legally encoded?” Gorbachev replied: “The topic of ‘NATO expansion’ was not discussed at all, and it wasn’t brought up in those years. … Another issue we brought up was discussed: making sure that NATO’s military structures would not advance and that additional armed forces would not be deployed on the territory of the then-GDR after German reunification. Baker’s statement was made in that context… Everything that could have been and needed to be done to solidify that political obligation was done. And fulfilled.”
[1] https://www.brookings.edu/blog/up-front/2014/11/06/did-nato-...
Every country can make their own decisions regarding their international treaties and alliances. The NATO expansion is also not something that’s happening against the will of the people in eastern countries. After the Crimea annexation, most countries in that sphere of influence turned anti-russia and more pro-nato. The majority of Ukrainians is currently also pro joining the NATO.
> Since June 2014, polls showed that about 50% of those asked supported Ukrainian NATO membership. Some 69% of Ukrainians want to join NATO, according to a June 2017 poll by the Democratic Initiatives Foundation, compared to 28% support in 2012 when Yanukovych was in power
“not ready to deploy” in 1990, "could not foresee circumstances” in 1991. These aren't open-ended commitments, but exactly the opposite.
Agreements regarding matters of such strategic gravity are always written down and signed by the involved parties. The expansion of NATO clearly was and remains as strategic a concern (to all parties) whether then or now. Note, for example, Russia's current demand for a "written legally binding response".
So we are either to assume Soviet team (Gorbachev et al.) were either incompetent or assets of the West, or, USSR capitulated and was not in a position to make legal binding demands regarding NATO and had to be satisfied with warm non-binding backroom reassurances.
I think it is the latter, and now, post Soviet Russia (caught between a pincer of Europe and China) believes it has a stronger hand and wants to re-negotiate.