Editing Umayyad Caliphate (section)

====Diwan al-Barid====
{{main|Barid}}

Mu'awiyah introduced the postal service, Abd al-Malik extended it throughout his empire, and Walid made full use of it. Umar bin Abdul-Aziz developed it further by building [[caravanserai]]s at stages along the Khurasan highway. Relays of horses were used for the conveyance of dispatches between the caliph and his agents and officials posted in the provinces. The main highways were divided into stages of {{convert|12|mi|km}} each and each stage had horses, donkeys, or camels ready to carry the post. Primarily the service met the needs of government officials, but travelers and their important dispatches were also benefited by the system. The postal carriages were also used for the swift transport of troops. They were able to carry fifty to a hundred men at a time. Under governor [[Yusuf ibn Umar al-Thaqafi]], the postal department of Iraq cost 4,000,000 dirhams a year.