Start of less tolerant policy towards Christians and Jews by the Seljuk authorities in the Abbasid empire.

Tahir later declared independence from the Abbasid empire in 822 by omitting any mention of al-Ma'mun during a Friday sermon.

After the collapse of the Abbasid empire in about 940 Samarra was abandoned.

Even the Ottoman double-entry accounting method, merdiban, was inherited from the Abbasid empire.

He not only held Baghdad (the capital of the Abbasid empire), but extended his dominion into Mesopotamia and Persia.

Merdiban was an accounting method used by the Ottoman empire, Abbasid empire, and Ilkhanate; especially for recording tax payments and liabilities.

The Abbasid empire grew somewhat during the reign of al-Ma'mun.

This further indicates that the majority of the works cannot have been read while Photius was in the Abbasid empire.

Al-Bukhari traveled widely throughout the Abbasid empire from the age of 16, collecting those traditions he thought trustworthy.

The Great Caliphs: the golden age of the 'Abbasid empire.