Once Muhammad died and Umar taught those tribes who wanted to leave Islam a lesson (a lesson many of them wouldn't remember because they were dead) the Arabs went off and conquered most of the Middle East and North Africa shouting "Allahu Akbar". You could hardly blame them for thinking God must be on their side and there still seems to be lot of belief in the Muslim world that they should have conquered the whole world. Something went wrong but if they could just get back to the days of Muhammad conquests over non-Muslims will continue and all their problems will be solved. It wasn't only Muhammad's example and commandments to raid and steal but Allah, God Himself, promised them oodles and oodles of other peoples' goodies to steal:
God has promised that you will receive much booty. He has enabled you to receive this at this time and has protected you from enemies to make it an evidence (of the Truth) for the believers. He will guide you to the right path. And other (victories and much booty there are, He promises you) which are not yet within your power, indeed Allah compasses them, And Allah is Ever Able to do all things. - Quran (48:20-21)
The initial flood of conquest ended after 100 years but when new Muslim nations arose with great armies e.g., Seljuk Turks, Ottoman Turks, and Moguls, they reverted to the expansion of Islam through conquest. You can't make omelettes without breaking eggs and you can't get booty without killing and stealing but Allah doesn't seem to give a fuck. But if successful warfare was a sign of God's approval, the Mongols conquered a lot more of the world than the Arabs and killed an awful lot of Muslims doing it and the European countries conquered and colonised the Muslim world in the 19th century and did it quite easily at that. Is it the Muslims who lost the plot or was Allah just another wannabe Lord of the Universe like Anat, Ashur, Baal, Huitzilopochtli, Ishtar, Marduk, Odin or Sekhmet?
Though the myth is that you either became a Muslim or you were killed this "choice" was only offered to "pagans" and in the early years the Muslims didn't want new converts. That would just make their protection racket less profitable. There would be less money to be extorted from fewer dhimmis to be shared amongst more Muslims. Where's the profit in that?
The early Muslim conquerors did not have much option about mounting their camels and heading out to greener pastures. Many Arabian tribes had joined the ummah because Muhammad was obviously on the way up and he was a dangerous man to cross. Those who had attempted to leave at his death were severely chastised in the Ridda Wars by forces led by Khalid ibn al-Walid, the so-called Sword of God who never lost a battle. Led by fear, religion or the wish for booty they headed for greener pastures.
Muslims believe that the conquests that began the "Golden Era of Islam" came because of the obedience of the salaf. It is remembered as a time when Muslims obeyed Allah and Allah blessed them with Islamic dominance. Like all such dreams of a Golden Age there is some truth in this myth. The foundations of radical Islam lie in the expectation of continual Islamic dominance and the nostalgic notion of an Islamic Golden Age compared with modern Islamic powerlessness. Radical Muslims believe if they obey Allah and imitate Muhammad's actions, Allah will bless them with victory.
Fighters for ISIS are under no compulsion and have little reason to expect either booty or success knowing that the forces of the West have had little trouble crushing Islamic armies for the past two hundred years. Only belief in the Islam of Muhammad's time can be their driving force. Muhammad demanded Muslims fight and Allah promised that if they were killed, they'd go straight to heaven and enjoy sex with many, many virgins and be able to drink wine legally in the Quran, Surah 78 (The Great News), Ayat 31-34.
ISIS and other caliphate-crazies are determined that in stage 1 they will at least reconquer the lands that were once ruled by a Muslim Caliph.
- Destiny Disrupted - Tamim Ansary
- Fields of Blood - Karen Armstrong
- The Legacy of Jihad: Islamic Holy War and the Fate Non-Muslims - Andrew G. Bostom
- Islam and Terrorism: The Truth About ISIS, the Middle East and Islamic Jihad - Mark A. Gabriel
- In the Shadow of the Sword: The Birth of Islam and the Rise of the Global Arab Empire - Tom Holland
- In God's Path: The Arab Conquests and the Creation of an Islamic Empire - Robert G. Hoyland
- The Lost History of Christianity: The Thousand-Year Golden Age of the Church in the Middle East, Africa, and Asia - and How It Died - John Philip Jenkins
- Islamic Imperialism - Efraim Karsh
- The Great Arab Conquests: How the Spread of Islam Changed the World We Live In - Hugh Kennedy
- The Looming Tower: Al Quaeda and the Road to 9/11 - Lawrence Wright
- Answering Jihad: a better way forward - Nabeel Qureshi