Raja Dahir (663 – 712 CE) was the last Hindu ruler of Sindh in present-day Pakistan. In 711 CE his kingdom was invaded by the Umayyad Caliphate led by Muhammad bin Qasimwhere Dahir died while defending his kingdom.
According to the Chachnama, the Umayyad campaign against Arori Raja Dahir was due to a pirate raid off the coast of the Sindhi coast that resulted in gifts to the Umayyad caliph from the king of Serendib(Old name of Sri Lanka) being stolen.
Throughout his reign, Maharaja Dahir had to face invasions from the Umayyad Caliphate which had grown quite powerful by that time.
According to Chachnama and the Arab historian Biladhuri, Dahir defeated the Arabs twice in pitched battles during the twin battles of Debal in which the invading Arab commanders Ubaidullah and Budail or Bazil were killed by Sindhis under Dahir’s son Jaisiah.
Jaisiah later appointed his own chief or Thakur who governed on his behalf. According to Chachnamah, when the news of Bazil’s death was relayed to Hajjaj, he became very sad and full of rage.
This led to the fateful expedition by Muhammad bin Qasim. Before the Battle of Aror, Maharaja Dahir is said to have given this speech as per Chachnama.
“I am going to meet the Arabs in open battle, and fight them as best as I can. If I crush them, my kingdom will then be put on a firm footing. But if I am killed honourably, the event will be recorded in the books of Arabia and India and will be talked about by great men. It will be heard by other kings in the world, and it will be said that Raja Dahir of Sindh sacrificed his precious life for the sake of his country, in fighting with the enemy.”
The primary reason cited in the Chach Nama for the expedition by the governor of Basra, Al-Hajjaj ibn Yusuf, against Raja Dahir, was a pirate raid off the coast of Debal resulting in gifts to the caliph from the king of Serendib (modern Sri Lanka) being stolen. Meds (a tribe of Scythians living in Sindh) also known as Bawarij had pirated upon Sassanid shipping in the past, from the mouth of the Tigris to the Sri Lankan coast, and now they were able to prey on Arab shipping from their bases at Kutch, Debal and Kathiawar.
Hajaj’s next campaign was launched under the aegis of Muhammad bin Qasim. In 711, bin Qasim attacked at Debal and, on orders of Al-Hajjaj, freed the earlier captives and prisoners from the previous (failed) campaign. Other than this instance, the policy was generally one of enlisting and co-opting support from defectors and defeated lords and forces. From Debal, bin Qasim moved on to Nerun for supplies; the city’s Buddhist governor had acknowledged it as a tributary of the Caliphate after the first campaign and capitulated to the second. Qasim’s armies then captured Siwistan and received allegiance from several tribal chiefs and secured the surrounding regions. His combined forces captured the fort at Sisam and secured the region west of the Indus River.
By enlisting the support of local tribes such as the Meds and also the support of the Buddhist rulers of Nerun, Bajhra, Kaka Kolak and Siwistan as infantry to his predominantly-mounted army, Muhammad bin Qasim defeated Dahir and captured his eastern territories which were added into the Umayyad Caliphate.