Excerpts from Books and Wikipedia
"The Anarchy at Samarra was a period of extreme internal instability from 861 to 870 in the history of the Abbasid Caliphate, marked by the violent succession of four caliphs, who became puppets in the hands of powerful rival military groups.
The term derives from the then capital and seat of the caliphal court, Samarra. The "anarchy" began in 861, with the murder of Caliph al-Mutawakkil by his Turkish guards. . . . Although the Abbasid Caliphate was able to stage a modest recovery in the following decades, the troubles of the "Anarchy at Samarra" inflicted great and lasting damage on the structures and prestige of the Abbasid central government, encouraging and facilitating secessionist and rebellious tendencies in the Caliphate's provinces." [Wikipedia]