The main thesis of Donner’s book is that the early Islamic movement was an ecumenical (a universal) movement that included all monotheists. As evidence, he cites the extant documents (though admittedly few) from the early Islamic era (610 to 690 AD) in where early Muslims mostly use the word al-mu’mineen (the believers) to address themselves, and even when the word muslimeen is used, it is used in the context of its true meaning, i.e. the ones who submit to one God. He cites the early coins issued by Muslims, all of which contain only the first half of the modern Muslim shahadah and do not mention the prophet Muhammad (these coins even contained images, and later the image of an Arab standing with a sword about which scholars dispute if it is the image of prophet Muhammad or the caliph). The word khalifa (caliph) was never used by early leaders of the movement, instead the only word used was amir al-mu’mineen (commander of the believers). Secondly, even all the works written by non-Muslims addressing these nomadic conquerors cite that these people use the words al-mu’mineen or al-muhajiroon (the migrants) to address themselves. Then there is proof that early Muslim armies included Christian and Jewish tribes, mostly Monophysite and Nestorian Christian tribes, in their ranks. He also concludes that, despite the reports (mostly Christian) of looting and destruction by Muslim armies, there may have been looting and pillage and seizing of slaves (more than 4000 slaves worked at caliph Muawia’s properties at Yamama) but there is no archeological proof of major destruction of properties (except in Tripoli in modern Lebanon, which, after a prolonged siege, was completely evacuated of its Christians by Muslims and repopulated with Jews), instead there were churches built at many sites after the occupation of Muslims. It was late only during the period of Umayyad caliph Abd al-Malik (r. 685-705) that coins were issued with the second part of shahadah along with the name of prophet Muhammad (which also shows their nonchalant attitude towards the name of God and prophet and Qur’anic ayahs). It was, Donner believes, an effort by the now victor Muslims to separate themselves from the defeated and vanquished population of Christians, Jews, and Zoroastrians (though many of them kept working as high ranking officers in Muslim bureaucracies). Lastly, some thoughts on Muslim civil wars (during the second of which Makkah and Medina were sieged twice by Muslim armies and Kaabah was burned to the ground): It was ibn Taymiyyah who in the fourteenth century conferred the title of khalifa-e-rashidun (the rightly guided caliphs) on the first four caliphs, but I wonder if the Muslims alive during the era of the first four caliphs would have agreed. It is strange that for an empire that had conquered half of the known world, nobody came to the rescue of caliph Usman, in fact many Muslims left Medina for Makkah as his house was seized. It shows that he was indeed deeply unpopular because of his policy of awarding important governorships to family members. Even Ali, by the end of his life, had no help from any of the major Muslim sections of army. Hijaz, Syria, Egypt, and most of Iraq had already aligned against him. Perhaps there was a reason he had been repeatedly ignored by the Muslim shuras for the title of the amir al-mu’mineen. Also, the practice of cursing the opposing caliph during Friday sermons was actually started by Ali, and then continued by Umayyad caliphs who issued decrees to curse the caliphs Usman and Ali.
PS: Caliph Mu’awiah in one of his letters to the Arab governors of Persia: “Be watchful of Persian Muslims and never treat them as equals. … As far as possible, give them smaller pensions and lowly jobs. In the presence of an Arab, a non-Arab shall not lead prayers, nor are they to be allowed to stand in the first row of the prayer.”