The Islamic Revolution surprised senior U.S. policymakers as well as the Shah of Iran, Mohammad Reza Pahlavi. On the eve of revolution, Iran—a key U.S. ally—seemed relatively stable despite bouts of urban terrorism in the early and mid-1970s. At the first signs of escalating unrest in early 1978, neither Iranian nor U.S. officials considered the possibility that Iran’s armed forces, the largest and most modern in the region (next to those of Israel), would prove unable to deal with whatever trouble lay ahead. The fall of the Shah a year later, therefore, raised searching questions regarding the role of the armed forces during the crisis and its failure to quash the revolution. The recent emergence of popular protest movements that have overthrown authoritarian regimes in Tunisia and Egypt—and that are challenging similar regimes in Libya, Yemen, Bahrain, and Syria—has revived memories of the Shah and his fall. These developments have again raised questions regarding the role of armed forces during revolutions and whether Iran’s experience during the Islamic Revolution and after holds relevant lessons for current developments in the Middle East.