This book examines the justification for using armed force throughout Islam's history. Special emphasis will be made to the following three terms, harb, jihad, and qital. These three words translate into war, struggle, and fight respectively. Not only are these terms the catalyst for the expansion of Islam in its first century, 632 to 732, but they have also contributed to many ideologies. The origins for such ideas begin in the seventh century and Islam's most prominent religious figure, Mohammed. It is only fitting that the first chapter of this endeavor starts with his life and the reasons why he went to war with others. As his life showed, he never declared a "jihad" on others, a term that is used constantly in the media. It is important to remember that according to Muslims, Mohammed never did anything out of his own opinion; it was all done with the endorsement of God. The Qur'an and Ahadith will also be examined, as they are the major sources for justifying and conducting war. After the death of Mohammed in 632 however, armed force began to take on a different meaning. This work covers Mohammed, the Kharijites, the Assassins, Ibn Taymiyya, Sayyid Qutb, al-Jihad, and al-Qaeda, with emphasis placed on Mohammed and Qutb as key figures, and their respective justifications for using or writing about resorting to armed force as a means to an end. During this book, comparisons will be made between all of the before-mentioned Muslims and their respective reasons for fighting or writing about the use of armed force. It is the main thesis of this work that violence committed in the name of God by Muslims throughout Islam's history is based upon the need to end oppression and establish justice. This book differs itself from other written works by solely examining the life and works of individual Muslims and Islamist groups and their justification for resorting to armed force. Though this topic has gained momentum since the events of 9/11, it is the intention of this work to show that using armed force is not new, but a political instrument used to establish Shari'ah or Islamic law. The term "political" is used because for most Muslims, including all those mentioned in this book, believe that Islam is not just a personal belief system, like most in the West believe, but an ideology that is to be used for all times and for all facets of life.