Iran and Iraq, though neighbors for many centuries, share both a common and a contentious history. Though both are Muslim nations, they have long been divided by their differing affiliations with the Shia and Sunni branches of Islam and by a cultural tension between Persian and Arab. These tensions have occasionally erupted into all-out warfare, most recently in the 1980s, when half a million Iraqis and Iranians were killed in a decade-long war. Today, however, following the toppling of the repressive Sunni dictator Saddam Hussein, Iraq’s previously oppressed Shia majority is forging ties with Shia-dominated Iran and creating a new, potentially destabilizing balance of power in this part of the Middle East. This book explores the long, rich, complex, and charged history between these two Muslim nations and analyzes what path they seem to be heading down in the future, a journey that has weighty consequences for the western world and the United States.