Since the Islamic Revolution in Iran in 1979, a priority of U.S. policy has been to reduce the perceived threat posed by Iran to a broad range of U.S. interests. In 2014, a common enemy emerged in the form of the Islamic State organization, reducing gaps in U.S. and Iranian interests, although the two countries have somewhat differing approaches over how to try to defeat the Islamic State. During the 1980s and 1990s, U.S. officials identified Iran's...