In 750 CE, the last Umayyad caliph Marwan II was defeated by the Abbasid As-Saffah in the Battle of the Zab on the banks of the Khazir River, a tributary to the Great Zab. When the Mongols swept over Iraq in the 13th century and sacked Erbil, many survivors sought a refuge in the inaccessible valleys of the Great Zab. The Sapna Valley was home to both Christian and Muslim communities, as evidenced by Christian artefacts found at Zawi Chemi Shanidar. During the 19th century, the area was controlled by local Kurdish leaders. During World War I, heavy fighting took place in the area, and Rowanduz was pillaged by Russian soldiers in 1916. Following World War I, episodes of heavy fighting took place between the Barzani tribe – striving for the establishment of an independent Kurdish polity – and several other Kurdish tribes, and between the Barzanis and the Iraqi Government. The last of these uprisings started in 1974 and led to heavy bombardments of towns and villages in the Great Zab basin.