Russia/Ukraine tensions - Any concern?

NATO expansion eastward since 1990, “Who promised what to whom on NATO expansion?” according to declassified US, Soviet, German, British and French documents.

History and documents

Did the United States really promise the Soviet Union during the 1990 negotiations on German reunification that NATO would not expand into Eastern Europe? Since the end of the Cold War, an array of Soviet/Russian policymakers have charged that NATO expansion violates a US pledge advanced in 1990 but some Western scholars and political leaders dispute that the United States made any such commitment.

US Secretary of State James Baker’s famous “not one inch eastward” assurance about NATO expansion in his meeting with Soviet leader Mikhail Gorbachev on February 9, 1990, was part of a series of assurances about Soviet security given by Western leaders to Gorbachev and other Soviet officials (including Boris Yeltsin) throughout the process of German unification in 1990 and on into 1991.

These documents show that multiple national leaders were considering and rejecting Central and Eastern European membership in NATO as of early 1990 and through 1991. The discussions of NATO in the context of German unification negotiations in 1990 were not at all narrowly limited to the status of East German territory and that subsequent Soviet and Russian complaints about being misled about NATO expansion were founded in written contemporaneous memos and telegrams at the highest levels. 

The documents reinforce former CIA Director Robert Gates’s criticism of “pressing ahead with expansion of NATO eastward in the 1990s, when Gorbachev and others were led to believe that wouldn’t happen.” The key phrase, buttressed by the documents, is “led to believe.”

https://greatpowerrelations.com/not-one-inch-eastward/#:~:text=US%20Secretary%20of%20State%20James%20Baker%E2%80%99s%20famous%20%E2%80%9Cnot,German%20unification%20in%201990%20and%20on%20into%201991.