Almost all western and other developed states use Principles of War as guiding ideas for military practitioners (especially those who serve at the operational and tactical levels) on how best to use combat power in order to gain maximum advantage. These Principles of War are virtually ubiquitous in cadet and officer colleges and in doctrine manuals. Islamic law, on the other hand, has nothing comparable, and least nothing from the modern world. It has always seriously and proactively engaged with ideas about how to ensure that war is fought for morally just causes. Yet, since the medieval period, Islam has not updated its thoughts on what principles might best enhance combat effectiveness in order to win battles and wars with the maximum effectiveness, the minimum use of force and the minimum likelihood of harm to the innocent. This study investigates whether one can draw such principles from the Qur’an and the life of the Islamic Prophet Muhammad that might serve as guidelines for Islamic armed forces in the twenty-first century, an era dominated by careless disregard for human life and by what is euphemistically called Collateral Damage. Within the earliest extant Arabic sources, this study identifies nine principles ― these being Virtuous Objective, Legitimacy, Unity of Command and Effort, Consultative Decision-Making, Offensive Action, Defensive Security, Morale, Restraint, and Deception ― that were integral in the warfighting of the Prophet. The author hopes that the analysis might, if widely read in the right circles, prompt further thought and research within Islamic states and their militaries so that something like an agreed set of Islamic Principles of War could eventually emerge and be of utility.