It is not just Russian President Vladimir Putin who has accused the western NATO members of having deceived Russia about their plans for NATO's eastward expansion. Discussions of the strained relationship between Russia and NATO often turn to how NATO's eastward expansion in 1999 and 2004 broke a promise made to the Soviet Union in the negotiations that led to of German reunification. Judging whether NATO's extension beyond its 1991 borders represents a broken promise or agreement is a fundamental moral assessment of the defense alliance. Declassified documents clearly show that Gorbachev was repeatedly verbally assured that NATO would not expand eastwards. Both in national jurisdiction and international politics, verbal promises and agreements can also acquire legal validity. Even legally non-binding agreements are regarded as essential instruments in international politics.
The question remains, however: Could Russia assume on the basis of Western assurances that NATO would not extend its sphere of influence further east? To what extent was NATO's eastward expansion a broken promise or even a breach of an agreement? Following NATO's eastward expansion, Russian confidence in the intentions of Western states was damaged by its operation 'Allied Force' and the new strategic concept. This did not change even after 1999: further rounds of enlargement (e.g., plans to accept Ukraine and Georgia as NATO member states) and the advanced US missile defense shield further undermined relations with Russia. Russia had no real voice in the negotiations with either the US or NATO. Only one thing has changed: with the election of Putin in 2000, Russia set off once again on its nationalist path, full of self-confidence.