Caliphate under Banu Umayyad rule
According to Berzin, Umayyad interest in the region occurred because of attacks from Sindh Raja Dahir on ships of Muslims and their imprisonment of Muslim men and women.[1] They had earlier unsuccessfully sought to gain control of the route, via the Khyber Pass, from the Turki-Shahis of Gandhara.[1] But by taking Sindh, Gandhara's southern neighbor, they were able to open a second front against Gandhara; a feat they had, on occasion, attempted before.[1]
According to Wink, Umayyad interest in the region was galvanized by the operation of the Meds and others.[2] Meds (a tribe of Scythians living in Sindh) had pirated upon Sassanid shipping in the past, from the mouth of the Tigris to the Sri Lankan coast, in their bawarij and now were able to prey on Arab shipping from their bases at Kutch, Debal and Kathiawar.[2] At the time, Sindh was the wild frontier region of al-Hind, inhabited mostly by semi-nomadic tribes whose activities disturbed much of the Western Indian Ocean.[2] Muslim sources insist that it was these persistent activities along increasingly important Indian trade routes by Debal pirates and others which forced the Arabs to subjugate the area, in order to control the seaports and maritime routes of which Sindh was the nucleus, as well as, the overland passage.[3] During Hajjaj's governorship, the Mids of Debal in one of their raids had kidnapped Muslim women travelling from Sri Lanka to Arabia, thus providing a casus belli to the rising power of the Umayyad Caliphate that enabled them to gain a foothold in the Makran, Balochistan and Sindh regions.[2][4]
Also cited as a reason for this campaign was the policy of providing refuge to Sassanids fleeing the Arab advance and to Arab rebels from the Umayyad consolidation of their rule.
All the above reason have their own importance for a first attack on Sindh. but immediate causes for the conquest of Sindh was the plunder of the gifts of