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.