Why does Josef Stalin matter?

Why is Stalin, Josef Stalin, Communist dictator of the Soviet Union for three decades, so important? What can we learn from him? What can we learn about socialism / communism, and tyranny? Stephen Kotkin, author of Stalin: Waiting for Hitler, 1929-1941, and a recognised authority on Stalin and his influence, discusses these things with Peter Robinson of the Hoover Institute at Stanford University. If you want to know about the terrible effects of Marxism, this is worth your time. This deals with Stalin during the time 1929 to 1941.