This book is part of the PhD thesis presented by Dr Muhammad Khair Haikal at the Imam Al-Awzaa'i Islamic studies faculty in 1412 AH on the subject of Jihaad during the early period of Islam in addition to the Islamic Fiqh in relation to the contemporary period. The Thesis was written in Arabic in over 2000 pages spanning over seven volumes. This is the English translation of Volume one of the thesis. The supervisory committee for this thesis had said that if there was a level above 'Imtiyaaz' (Excellence) they would have awarded it to this thesis and its author. It is perhaps the most extensive and detailed research on the subject of Jihad in Islam to have been undertaken. The author has painstakingly made detailed references to the source of Islamic rulings and evidences of the Quran and the Sunnah. He has also referred to the well known Imams, Mujtahideen and Fuqaha of the Ummah as part of his research. He has also discussed the situation of the modern day thinkers on the subject of Jihaad and the ideas and views of various Islamic groups on the subject. Part One of Volume One covers the research on the reasons for the wars which occurred prior to Islam, the definition of Jihad linguistically, Shar'an (according to the Shara'), 'Urfan (according to the custom) and Istilaahan (according to terminological convention). The second part of the Volume One covers twelve researches: The First Study: Qitaal Ahl-ur-Riddah (Fighting the apostates)The Second Study: Qitaal Ahl-ul-Baghyi (Fighting against the people of rebellion)The Third Study: Qitaal Al-Muhaaribeen / Quttaa' At-Turuq (Highway robbers)The Fourth Study: Fighting (Al-Qitaal) in defence of the private sanctities: An-Nafs (the life), Al-'Ird (the honour) and Al-Maal (property)The Fifth Study: Fighting (Al-Qitaal) in defence of the public sanctities (Al-Hurumaat Al-'Aammah) within the Islamic societyThe Sixth Study: Fighting (Al-Qitaal) against the Inhiraaf (deviation) of the Haakim (ruler)The Seventh Study: Qitaal ul-Fitnah (Fighting of disorder)The Eighth Study: Qitaal Mughtasib As-Sultah (Fighting the usurper of the authority)The Ninth Study: Qitaal Ahl udh-Dhimmah (Fighting the people under contract of protection)The Tenth Study: Qitaal Al-Ghaarah (fighting by raids or attacks) for the purpose of seizing the property of the enemyThe Eleventh Study: Al-Qitaal (fighting) to establish the Islamic State and protect itThe Twelfth Study: Al-Qitaal (fighting) for the sake of the unity of the Islamic lands