In the question Did NATO promise Gorbachev not to accept membership applications from former Warsaw Pact nations?, which made a factually wrong claim (that the GDR joined NATO in 1990), I made a comment along the lines of...
The GDR did not join the NATO, ever. What happend there (in 1990) was that the GDR ceased to exist, and the FRG expanded to include the five federal states constituting the territory of the former GDR. That was an eastward expansion of NATO borders, but not the accepting of a former Warsaw Pact nation into NATO. If such a promise was made (which I won't judge in a comment), the first case of it being broken would be the 1999 inclusion of Poland, Hungary, and the Czech Republic.
This is written from memory, as the comment was removed without notification or explanation.
The OP actually edited his question to reflect this input, so it was helpful. I also feel it was not offending or violating any rules of conduct.
I would like to know why the comment was removed. If it happened because the OP edited his question, I would like to point out that SE gives badges for leaving helpful comments, and it strikes me as odd that such a comment should be removed by moderators.
Especially as later comments are discussing the very same subject.