In a book of keen perception, Ulam examines one hundred years of Russian revolutionary thought and the people who shaped and were caught up in it. Ulam displays an unusual ability to get at the central facets of the Soviet mind as it evolved and was encapsulated in history. We understand more fully why the Russians signed a treaty with Hitler; feared Titoism; built a Berlin Wall, rattled missiles, then signed a nuclear-test-ban treaty with President Kennedy; and why detente was fostered when Nixon was President.