After Communist regimes in Eastern Europe collapsed twenty years ago and the Soviet Union disintegrated two years later, immense opportunities for archival research opened. Even though serious obstacles to archival work have persisted in Russia (which houses the central repositories of the Soviet regime), the archives of nearly all of the former Warsaw Pact countries are now fully or at least largely open. As a result, scholars have been able to explore many aspects of the Warsaw Pact that could only be guessed at in the past, including questions of military planning, force preparations and operations, nuclear command arrangement, and civil-military issues.