Since the beginning of the seventh century, Islamic law has played an essential role in protecting the personal, economic, judicial, and political rights of civilians during armed conflict. Fourteen centuries before the Universal Declaration of Human Rights was drafted in 1948, it had already initiated a human revolution consisting of a set of human principles. In addition, Islamic law has made a significant contribution to international humanitarian law (IHL). This paper focuses on two specific legal constructs in warfare: the definition of the combatant and the principle of distinction. This article comparatively examines how these two laws deal with different aspects of war that fall under jus ad bellum, jus in bello, and jus post bellum. A comparative analysis of the various elements and aspects of just war theory in Islamic and contemporary international law provides a much deeper understanding of its limitations. We can safely conclude that there is a unique relationship between the Islamic law of war and IHL.