MUSLIM INVASIONS

In 712 AD, AI Hajjaj, the Governor of Basra, led an expedition against Sindh's ruler Dahir, under his nephew and son-in-law, Muhammad-bin-Qasim. This expedition put Sindh under the Arabs. 
      The cause of this expedition was neither the desire for territorial expansion nor religious. The king of Ceylon had sent some gifts to the king of Turkey which were looted at Debal in Sindh by the pirates. The ruler of Sindh, Dahir, refused to compensate the loss by showing his ignorance to the incident. This emerged AI Hajjaj and he attacked Sindh.
      However, the Arabs failed to build a permanent empire in India. Several factors were responsible for this.
Imprisonment of Muhammad bin Qasim by the new Khalifa
New Khalifa's indifferent attitude towards desert Sindh province
Diversion of Arab attention due to fight over Khilafat or Caliphate
Bravery and Heroism of Indian ruler
Long distance between Baghdad and Sindh.
Impact of Arab Rule in Sindh
Conversion of Sindh population to Islam, albeit on a very limited and temporary scale
Laying the foundation of Islam in India
Introduction of formal slavery system in India
Promotion to Arab trade.
New Arab settlements on sea-coast