Uskāf Banī Junayd,[1] also Iskāf,[2] was an ancient and medieval city of Iraq, located on the Nahrawan Canal at the present site of Sumāka.[3] In its heyday, during the Sasanian period and early Islamic caliphates, Uskaf was the largest city in the Diyala basin;[4] however, it declined sharply after the Samarran period and was abandoned by the early 1100s.[5]
Uskaf was inhabited during the Achaemenid and Parthian periods, but on a much smaller scale than in later periods.[6] Although not mentioned by name in contemporary accounts, Uskaf was a significant urban center during the Sasanian period. It grew to an area not much smaller than Ctesiphon itself.[7] A massive weir at the site of al-Qantara was constructed just north of Uskaf during the Sasanian period; however, it does not seem to have been in use for that long during this period.[8]
Uskaf was the largest city in the Diyala basin both in the Sasanian and early Islamic periods.[9] During this time, the city became known as "Bani Junayd" after a powerful local family known for its hospitality.[10] [11] Writing in the early 1200s, well after the city's decline, Yaqut al-Hamawi noted that many learned men had come from Uskaf, reflecting the city's prosperity in its heyday.[12]
After the Samarran period, however, Uskaf went into a dramatic decline, with the physical area of the city shrinking to a mere 5% of its greatest size in the Sasanian and early Islamic periods.[13] During this period, the volume of water flowing through the Nahrawan canal decreased substantially, leading to an increased reliance on the weir at al-Qantara as a source of water for irrigation. The weir artificially raised the canal's water level above its location, but dramatically reduced the water level below it.[14]
The final construction at Uskaf dates from the late 11th century, and the site appears to have been abandoned shortly thereafter.[15] By the early 1200s, Yaqut al-Hamawi wrote that the lands around Uskaf had gone completely out of cultivation.[16]