Listen in to a debate on the fear shared by the Soviet Union and United States of the enemy within, as featured on the weekly CNN program "Postscript" -- which accompanies the COLD WAR series.

CNN World Affairs Correspondent Ralph Begleiter, Russian historian Vladislav Zubok and American scholars Timothy Naftali and Thomas Blanton consider the similarities between the Soviet purge trials and McCarthyism in the United States.

Dr. Vladislav Zubok is one of the leading historians of the Soviet side of the Cold War and the author of "Inside the Kremlin's Cold War." He has studied extensively in Soviet and American archives and has taught classes on the Cold War at Amherst College, Ohio University in Athens and Stamford University. In 1993, Zubok was employed by the Kennan Institute for Advanced Russian Studies in Washington, D.C., and since then has worked at the Norwegian Nobel Institute in Oslo and is now a fellow at the National Security Archive in Washington.

Timothy Naftali teaches at the University of Virginia. He is currently working on a book on U.S. counterespionage and is an Olin Fellow in International Security Studies at Yale University.

Thomas Blanton is executive director for the National Security Archive in Washington, D.C. The NSA is a non-governmental research institute providing information from U.S. government and official archives for scholars, journalists, members of Congress, lobbyists and others. Their research teases out documents still classified to give a complete picture of what really happened.