The Muslims suffered another major defeat in the Battle of the Defile in 731, in which they lost some 20,000–30,000 men, crippling the native Khurasani Arab army and necessitating the transfer of new troops from Iraq. In the years after the Defile, Samarkand too was lost and the Sogdians under Ghurak regained their independence, while Muslim military activity north of the Oxus River was severely curtailed: what little campaigning is mentioned in the contemporary sources before 735 concerns operations to maintain the allegiance of the principalities of Tokharistan in the upper Oxus valley.[7][8][9] In addition, the Umayyad authorities were preoccupied by the rebellion of al-Harith ibn Surayj, which broke out in early 734, spread quickly, and gathered the support of a large portion of the indigenous Iranian population.