History is thus a model for the use and edification of believers, a model and a warning; it links the temporal with the eternal. Everything historical is only a prelude. The medieval historian knows no periodisation, only simple categories for dividing up the material. This may be according to years (the annalistic format), according to the periods when rulers were in power, and also in the biographical literature according to ‘classes’, i.e. the generations of scholarly transmission.
The modern historian tries to describe the events of particular regions coherently, whilst at the same time bearing in mind relations and reciprocal influences with neighbouring territories and bringing to light overlapping processes in this he is searching for a structure, for the ‘universal’ in the multiplicity of data and facts. In the course of Islamic history, however, it becomes progressively more difficult to define periods of the whole Islamic world by important events or by developments which were common to Islam in general. The west (Spain and North Africa) and the Iranian east – even if formal loyalty to the caliph was maintained – led a life of their own from as early as the middle of the ninth century onwards.
In all periods there were external movements and internal developments which wide areas of the Islamic world experienced communally, but there were always regions, too, which remained untouched. Thus, for example the processes of nomadisation which began in the eleventh century, and which were unleashed in the east by the invasion of the Turcomans and in the west through the irruption of the HilÅl Bedouin into the Maghrib, are striking parallels but they have no deeper relationship with each other. On the other hand, the simultaneous return to doctrinal traditionalism in the west and in the east has a common basis, namely the decline of the religious authority of the caliphate and of its vassals. There is no doubt too that the Mongol invasion of the thirteenth century and the expansion of the Ottoman empire in the fifteenth and sixteenth centuries are events of wide-ranging importance and for that reason are really epoch-making.
Every broad division into periods can therefore be no more than an aid towards the arrangement of general synopses, and in order to achieve its aim must combine chronological and geographical divisions. Such definitions are questionable, since every period contains the beginnings of the following one and in the face of every crisis there is also continuity; but they are nonetheless useful. The following outline has above all the aim of illustrating the patterns and divisions usually drawn up by historians of Islam.
Iraq
