"Western leaders never pledged not to enlarge NATO, a point that several analysts have demonstrated. Mark Kramer explored the question in detail in a 2009 article in The Washington Quarterly. He drew on declassified American, German and Soviet records to make his case and noted that, in discussions on German reunification in the two-plus-four format (the two Germanys plus the United States, Soviet Union, Britain and France), the Soviets never raised the question of NATO enlargement other than how it might apply in the former German Democratic Republic" (GDR).
" Gorbachev replied: “The topic of ‘NATO expansion’ was not discussed at all, and it wasn’t brought up in those years."
https://www.brookings.edu/blog/up-front/2014/11/06/did-nato-promise-not-to-enlarge-gorbachev-says-no/
Who cares what Gorbachev speaks now? But that’s of course another lie. Here is another link for you.
“Washington D.C., December 12, 2017 – U.S. 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 cascade of assurances about Soviet security given by Western leaders to Gorbachev and other Soviet officials throughout the process of German unification in 1990 and on into 1991, according to declassified U.S., Soviet, German, British and French documents posted today by the National Security Archive at George Washington University http://nsarchive.gwu.edu/";.
President George H.W. Bush had assured Gorbachev during the Malta summit in December 1989 that the U.S. would not take advantage (“I have not jumped up and down on the Berlin Wall”)
The first concrete assurances by Western leaders on NATO began on January 31, 1990, when West German Foreign Minister Hans-Dietrich Genscher opened the bidding with a major public speech at Tutzing, in Bavaria, on German unification. The U.S. Embassy in Bonn (see Document 1) informed Washington that Genscher made clear “that the changes in Eastern Europe and the German unification process must not lead to an ‘impairment of Soviet security interests.’ Therefore, NATO should rule out an ‘expansion of its territory towards the east, i.e. moving it closer to the Soviet borders.’” The Bonn cable also noted Genscher’s proposal to leave the East German territory out of NATO military structures even in a unified Germany in NATO
This latter idea of special status for the GDR territory was codified in the final German unification treaty signed on September 12, 1990, by the Two-Plus-Four foreign ministers (see Document 25). The former idea about “closer to the Soviet borders” is written down not in treaties but in multiple memoranda of conversation between the Soviets and the highest-level Western interlocutors (Genscher, Kohl, Baker, Gates, Bush, Mitterrand, Thatcher, Major, Woerner, and others) offering assurances throughout 1990 and into 1991 about protecting Soviet security interests and including the USSR in new European security structures.
Having met with Genscher on his way into discussions with the Soviets, Baker repeated exactly the Genscher formulation in his meeting with Foreign Minister Eduard Shevardnadze on February 9, 1990, (see Document 4); and even more importantly, face to face with Gorbachev.
Afterwards, Baker wrote to Helmut Kohl who would meet with the Soviet leader on the next day, with much of the very same language. Baker reported: “And then I put the following question to him [Gorbachev]. Would you prefer to see a united Germany outside of NATO, independent and with no U.S. forces or would you prefer a unified Germany to be tied to NATO, with assurances that NATO’s jurisdiction would not shift one inch eastward from its present position? He answered that the Soviet leadership was giving real thought to all such options [….] He then added, ‘Certainly any extension of the zone of NATO would be unacceptable.’” Baker added in parentheses, for Kohl’s benefit, “By implication, NATO in its current zone might be acceptable.” (See Document 8)
Well-briefed by the American secretary of state, the West German chancellor understood a key Soviet bottom line, and assured Gorbachev on February 10, 1990: “We believe that NATO should not expand the sphere of its activity.” (See Document 9)
There are much more at link but that doesn’t even change much. The problem in this case is the expansion of NATO by itself which wasn’t justified at all.