This book evaluates the life and empire of the pivotal yet controversial and poorly understood Byzantine emperor Heraclius (AD 610-641), a contemporary of the Prophet Muhammad. Heraclius' reign is critical for understanding the background to fundamental changes in the Balkans and the Middle East, including the emergence of Islam, at the end of antiquity. Heraclius captured and lost important swathes of territory, including Jerusalem and Syria and Egypt. Skills in exploiting divisions within the ranks of his opponents, and encouraging the switching of sides and the breakdown of morale, provided Heraclius with his greatest triumphs, yet they proved to be of little value when he finally confronted the early Islamic conquests. The author synthesizes diverse primary sources, including those in Greek and Arabic, in the light of more recent historical scholarship. The varied Mediterranean and Middle Eastern context stretches from North Africa to Syria, Armenia and what is modern Iraq.