ARAB INVASION OF SIND(MEDIEVAL HISTORY)
In 712 AD, Mohammad-bin-Qasim was sent by Al-Hajaj, the governor of Iraq with the permission of Caliph Walid(Ummayad dynasty) to conquer Sind. Mohammad-bin-Qasim was a 17-year-old boy and the general of Ummayad dynasty and the nephew and son-in-law of Al-Hajaj. Before 710AD two attempts were made by Al-Hajaj in the year 637 C.E(Thaner\Bombay) and 644 C.E(Sind).
REASONS FOR INVASION
For plundering the wealth and the Arabs were attracted by the rich ports of Sind so they want control over it. For the expansion of Islam as Arabs adopted a new religion-Muslim. Another reason is that they were angry with Dahir(the ruler of Sind), who failed to check the pirates who plundered them.
Arabs got success due to the leadership of Mohammad-bin-Qasim and political and social disintegration of Sind as people were not happy with the Chach dynasty, and by social integration I mean there was no unity between religions.
Mahmud of Ghazni ascended in 998 C.E succeeds Shabutjeen(father). He belongs to the Yaminid dynasty and was the first ruler of his dynasty to call himself a sultan. He gave normal allegiance to Abbasid Caliph in Baghdad, and the Caliph in turn rewarded him with the titleYamin-ud-Daula(Right hand of the state). He did 12 or 17 invasions(1000-1025 AD) and he plundered the Somnath temple in 1025B C.E. He never appointed governor, plunder, and goes back so he never thought of a permanent empire. His last expedition was in 1027 C.E against jats and he died in the year 1030 C.E. The Ghazni dynasty declined giving rise to the Ghori dynasty.
Muhammad Ghori brought Ghazni under his control and he was the real founder of Muslim power in India.