• TL;DR from article:

    Under the 1997 NATO-Russia Framework Agreement, NATO has pledged not to permanently deploy significant forces in central and eastern Europe […] However, Russia has committed to refrain from aggression against its neighbours and is not complying […] As a result […] the Alliance is no longer bound by restrictions on the expansion of forces in its eastern flank.

    • Huh, it took Russia just a little over a decade to break that agreement by invading Georgia. Looks like NATO has had plentiful justification for the past 14 years to declare Russia in breach of the agreement.