https://en.wikipedia.org/wiki/Treaty_on_Conventional_Armed_Forces_in_Europe

Agreement on Adaptation of the Treaty on Conventional Armed Forces in Europe (CFE-II)

The Agreement on Adaptation of the Treaty on Conventional Armed Forces in Europe (also known as the adapted CFE treaty) is a revision of the original treaty and was signed during the November 1999 Istanbul summit and took into account the different geopolitical situation of the post-Cold War era by setting national instead of bloc-based limits on conventional armed forces. NATO members refused to ratify the treaty as long as Russia refused to completely withdraw its troops from Moldovan and Georgian soil. While Russia partially withdrew troops and equipment from Georgia and Moldova, it did not do so completely as demanded by NATO. The linkage between the ratification of the adapted treaty and the complete withdrawal has no legal basis, but is rather a political decision made by NATO members.

Suspension by Russia

After Russia was not willing to support the US missile defense plans in Europe, Russian President Vladimir Putin called for "moratorium" on the treaty in his April 26, 2007 address. Then he raised most of his points for rewriting the treaty during the Extraordinary Conference of States Parties to the Treaty on Conventional Forces in Europe, held in Vienna on June 11–15 at Russia’s initiative.[14] As his requests were not met during this conference, Putin issued a decree intended to suspend the observance of its treaty obligations on July 14, 2007, effective 150 days later, stating that it was the result of "extraordinary circumstances (...) which affect the security of the Russian Federation and require immediate measures," and notified NATO and its members.[15][16] The suspension applies to the original CFE treaty, as well as to the follow-up agreements.