s a certain Ya'qub b. Da'ud, who, having insinuated
himself into the confidence of the caliph, especially by discovering the
hiding places of certain Alids, was afterwards (in 778) made prime
minister. The provincial governors in whom his father had placed
confidence, Mahdi superseded by creatures of his own.

In Khorasan many people were discontented. The promises made to them
during the war against the Omayyads had not been fulfilled, and the new
Mahdi did not answer at all to their ideal. A revolt in 160 under the
leadership of a certain Yusuf b. Ibrahim, surnamed al-Barm, was
suppressed by Yazid b. Mazyad, who, after a desperate struggle, defeated
Yusuf, took him prisoner and brought him in triumph to Bagdad, where he
with several of his officers was killed and crucified. In the following
year, Mahdi was menaced by a far more dangerous revolt, led by a
sectary, known generally as Mokanna (q.v.), or "the veiled one," because
he always appeared in public wearing a mask. He took up his abode in the
Transoxianian province of Kish and Nakhshab, where he gathered around
him a great number of adherents. After some successes, the pretender was
ultimately cornered at the castle of Sanam near Kish, and took poison
together with all the members of his family. His head was cut off and
sent to Mahdi in the year 163.

Mahdi had been scarcely a year on the throne when he resolved to
accomplish the pilgrimage to Mecca. The chroniclers relate that on this
occasion for the first time camels loaded with ice for the use of the
caliph came to Mecca. Immediately on his arrival in the Holy City he
applied himself, at the request of the inhabitants, to the renewal of
the curtains which covered the exterior walls of the Ka'ba. For a very
long time no care had been taken to remove the old covering when a new
one was put on; and the accumulated weight caused uneasiness respecting
the stability of the walls. Mahdi caused the house to be entirely
stripped and anointed with perfumes, and covered the walls again with a
single cloth of great richness. The temple itself was enlarged and
restored. On this occasion he distributed considerable largesses among
the Meccans. From Mecca Mahdi went to Medina, where he caused the mosque
to be enlarged, and where a similar distribution of gifts took place.
During his stay in that city he formed for himself a guard of honour,
composed of 500 descendants of the Ansar,[32] to whom he assigned a
quarter in Bagd