Book excerpt: The global war on terror (GWOT) and the battles with specific Islamist groups is, to some degree, a war of ideas. With a better understanding of Islamic concepts of war, peace, and Muslim relations with non-Muslims, those fighting the GWOT may gain support and increase their efficacy. The authors explain the principles of jihad and war and their conduct as found in key Islamic texts, the controversies that have emerged from the Quranic verses of war and peace, and the conflict between liberal or moderate Islamic voices and the extremists on matters such as the definition of combatants, treatment of hostages, and suicide attacks.