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The crisis is a succession of disasters that affected a vast region extending from the Atlantic Ocean to Central Asia between about 940 and about 1150. Between these two dates, the Byzantine Empire, the Eastern Christian principalities and the major Muslim states were shaken by deep political unrest and major economic crises. These disasters have resulted in a marked decrease in the importance of the Muslim and Byzantine worlds compared to India, China and Europe from the end of the Middle Ages.

The events that shook the Arab, Byzantine and Persian worlds during the crisis of the n, were only recently linked by historians. Previously, the major phases of the crisis were considered independently. A first attempt at systematization was made by Pierre Guichard in 1998. Then, in 2012, the Israeli academic, Ronnie Ellenblum proposes to link all these events by giving them a common climatic cause.

Thus, it is probably to be placed among the great general crises that have affected more or less vast areas of the world such as the collapse of the Mediterranean world at the end of the Bronze Age, Justinian's plague, the crisis of the late Middle Ages or the crisis of the late 19th century.

Causes
The various crises of the period 950-1150 received a lot of individual attention, their origins were sought in three different directions: a decline in agriculture, poor political management and the influence of the climate.

Agricultural hypothesis
In some regions, there is much evidence that since agricultural production in the Abbasside Empire collapsed since the establishment of the Caliphate. Thus, in Mesopotamia, the sum of taxes levied in rural areas had gone from dirham at the end of the year to the beginning of the year. This deterioration in production led to a destabilization of the countryside and a large number of revolts (especially those of the Zanj and the Qarmats) broke out in Iraq as soon as . These insurrectional movements, followed by others that later struck the cities, would have contributed to deepening the crisis by forcing part of the rural communities to migrate and causing significant damage to irrigation works, further reducing agricultural production in Mesopotamia. This decrease had already been noted by the Arab authors as early as .

The increased salinity of the fields due to too extensive irrigation work is a possible cause of the considerable decline in agricultural production between the Sassanide period and the Abbasside period. The elite who had emerged since the Muslim conquest, or who had persisted in spite of it, therefore found themselves unable to maintain their lifestyle without increasing their income on the countryside. The consecutive growth of taxes led Von Sivers to rural revolts against the level