NATO's expansion to the east is the West's biggest political mistake since the end of the Cold War. This is not only the official position of the Russian government but an opinion shared by scores of independent Russian, European, and US experts. The cost of this mistake is high, and it should be borne by those responsible for it: the United States and its allies. For the near future, Russia will remain aloof and will not undertake any significant political, economic, or military steps in response to the new situation. Nevertheless, the expansion of the Western alliance is and will continue to be one of the major problems for Russian foreign and national security policy. Obviously, the Russian factor has not been seriously taken into consideration by the NATO allies during the decision-making process, but it plays an important role and should be expected to have a deep impact on the alliance's enlargement and its future consequences.