Archives in which Joshua Shifrinson (Boston University) discovered a memo classified as "secret" dated 6 March 1991 (approximately five months after the 2+4 negotiations). The memo is about a meeting of the directors of the US, UK, French and West German foreign ministries in Bonn. According to the memo, Jürgen Chrobog, the Western German representative, stated that "during the 2+4 negotiations we made it clear that we [Germany] would not expand NATO beyond the Elbe . We cannot therefore offer Poland and the others NATO membership." Klaus Wiegrefe says that Chrobog may have confused the Elbe for the Oder, to which NATO was supposed to extend upon German unification. Bonn had never made it clear that NATO would not expand beyond the Elbe, According to , a German foreign minister at the time would never make a binding statement on behalf of NATO. Russian claims of the alleged 1990 assurances on a non-expansion of NATO to Gorbachev were again raised on the occasions of the annexation of Crimea by the Russian Federation in 2014 and the 2021–2022 Russo-Ukrainian crisis, during which the Russian President Vladimir Putin demanded a legal ban on Ukraine joining NATO, which both Ukraine and NATO refused, and the subsequent invasion of Ukraine by Russia. The invocation of this alleged non-expansion pledge was used by Russia to justify its open breach of the Budapest Memorandum but has been rebuffed by NATO. See also Allied Control Council Basic Treaty Bonn–Paris conventions Council of Foreign Ministers Four Power Agreement on Berlin Germany Treaty London and Paris Conferences Occupation statute Petersberg Agreement Notes References Further reading Trachtenberg, Marc. "The United States and the NATO Non-extension Assurances of 1990: New Light on an Old Problem?" International Security 45:3 (2021): 162–203. https://doi.org/10.1162/isec_a_00395 and online commentary on H-DIPLO 2021 External links Full text in English (PDF format; Published by Her Majesty's Stationery Office on the Foreign and Commonwealth Office website) Full text in English (HTML format; Published by U.S. Diplomatic Mission to Germany) Aftermath of World War II Allied occupation of Germany 1990 in France 1990 in Germany 1990 in the Soviet Union 1990 in the United Kingdom 1990 in the United States Treaties of the Soviet Union Soviet Union–United Kingdom relations Soviet Union–United States relations France–Soviet Union relations Germany–Soviet Union relations Germany–United Kingdom relations Germany–United States relations France–Germany relations Boundary treaties Germany Treaties of East Germany Borders of Germany German reunification Treaties