Since the Iranian Revolution more than thirty years ago, the Islamic Revolutionary Guard Corps (IRGC), also known as the Revolutionary Guard, has conducted covert and overt military operations, built an economic empire, and trained, financed, and guided terrorists to pursue one goal--the preservation and expansion of the Islamic revolution. Inside Iran the IRGC influences the country's politics, economy, and foreign policy, and controls its nuclear program. Outside Iran the operations of the IRGC and its proxies, including Hezbollah in Lebanon and Shiite militias in Iraq, have left a trail of...