Generally in the history books the cause of the Arab invasion to Sindh is described as the imprisonment of women and children of Arab families who were coming from Sri Lanka by the sea pirates near Debal, presumably by the approval of the ruler of Sindh. An Arab girl at the time of capture cried for help to Hajjaj, who was the governor of Basrah.On hearing about this incident and the plea of the girl, he decided to punish the ruler and get the Arab prisoners released. A thorough analysis reveals many weaknesses and flaws of the story. Hajjaj, a shrewd politician and experienced general who has been negatively portrayed in the history by the historians of the Abbasid period as a tyrant and despot because of his Umayyad affiliation, could not take action to invade Sindh merely on the cry for help of a girl .He was not the man to be carried away by emotions and sentiments. On the contrary, he took political decision coolly after weighing the pros and cons of the case.

Therefore, there were other important reasons that compelled him to undertake the venture. First all, the Arabs had made many attempts to conquer Sindh since the time of Hazrat Umar but failed to achieve their object because there was no immediate need to occupy it for military or political reasons. However, during the Umayyad period it became possible because, after the conquest of Makran, the land route became safe and a large army could be sent without any danger and obstacle. Moreover, by the time of the 8^th century, the Arab merchants had established close trade and commercial relations with the coastal towns of south India and Sri Lanka and established their settlements in a number of places. Therefore, the presence of sea pirates near the port of Debal and the capture of the ship alarmed the merchant community. Their concern was safety of the sea route. Apparently, that was the reason that Hajjaj decided to send expeditions to Sindh to conquer and to occupy it in order to protect the interest of the Arab merchants. .

Historians also give credit to Muhammad b. Qasim for the conquest of Sindh and especially emphasise his youth as a factor to his achievements. The close study of the Chuchnama or Fathnama shows that in reality, Muhammad b. Qasim was just a figure head and the real authority was in the hand of Hajjaj who conducted the whole expedition sitting in Basrah commanding the young general how to act, negotiate and tackle different problems. We find that Muhammad b. Qasim asked for everything to Hajjaj: how to deal with the vanquished people, how to cross-river, how to talk with the tribal chiefs and how to make arrangement in the battlefields. He never dared to take any action independently.

In this regard the decision of Hajjaj on the treatment of the Sindhi Hindus and Buddhists is very significant. When Muhammad b. Qasim asked him how should they be treated? Hajjaj wrote to him that they should be treated as people of the book like the Zoroastrians of Persia and after paying jizya, they should be given the status of Zimmis.That was the model that later on the Sultans of Delhi and Mughal Emperors adopted in India.

It is also evident from the original sources as al-Baldhuri and the Chuchnama that the main motive of the expedition was not religious but economic and political. It was the period when the Umayyad was busy in conquering Central Asia, North Africa, and Spain. The expansion meant acquiring more land and more resources. After the conquest of Multan, Muhammad b. Qasim got accumulated wealth from the city temple. Hajjaj happily reported to the caliph that he was paying back to the state treasury three times more what he had loaned for the expedition. This statement clearly shows the economic rather than religious or humanitarian interests of the conquest of Sindh.

Another question that requires analysis that how Islam spread in Sindh? The study shows that it spread not because of the efforts of the rulers but because of the social, political and economic reasons of those who converted to Islam. In Sindh, the majority of population was Buddhists and therefore, the control of Brahmanism was weak. The tribal system also did not integrate them into one coherent group. Thereby, this tribal division made easy for the people to convert and sought the support of the Arab rule against their rivals. We find a pattern of conversion in Sindh; once a tribal chief became Muslim, the whole tribe followed their chief and converted to Islam as an expression of their loyalty.

Another feature of the Arab conquest of Sindh is that in spite of the occupation and remaining a part of the Caliphate for 150 years, the Arabic language could not become the lingua franca. This is quite contrary to the other regions which came under the Arab control such as North Africa where the local languages were eliminated and Arabic became the predominant language of the people. Why did this not happen in Sindh? A close study shows that as a result of the Eastern conquests, the Arabic language kept its hegemony up to Iraq but Iran, Khurasan, and Central Asia resisted to accept Arabic and persisted to continue to speak their local languages. Sindh also followed the tradition of resistance and kept its local languages alive. In this connection, one can also ask the question about the different ethnic groups who were in the Arab army: whether they were Arabs or non-Arabs. If the majority of the settlers were non-Arabs, it was the major reason that Sindh could be incorporated in the Arab culture and retained its separate identity.