Dear All
Taking the 1400 years in full sweep, the first and the foremost issue is that of original source material, but for the times of Messenger Muhammad peace be upon him and his immediate successors, even these original sources are not available. The so-called original sources, Al-Tabri's history and Ibn-Ishaq's biography of Messenger Muhammad peace be upon him and the collected traditions were written more than 200 years after the event, without any previous written record. What happened to this previous record is perhaps a story by itself and needs to be researched. The funny thing is that subsequent historians and biographers continued to refer to these so-called -original- sources and till today no historian, Muslim or non-Muslim, has ever questioned the authenticity of Al-Tabri and Ibn-Ishaq.
Secondly, there is need to emphasize that the Ummayed dynasty, the Arab in character, remained men of action harmonius with their centuries old mode of living. The unleashing of this quality led to the conquest of vast lands from the Atlantic and the Pyrenes in the West to the Chinese frontier in Sinkiang in the East. Writing was not their main bastion. But when the Abbasides came to power with the support of the Persians and Khorasanians, the period of action and conquest ended and that of writing began. The writers of this period were predominantly Persians, who were hell-bent upon winning the war against the Arabs with their writings -and against the war, which they had lost in the battlefield.
Regards
Nawaz