Usually it is said that Islam spread in Hindustan (subcontinent) by the means of war and forceful conversion, while the truth is first Mosque of India was built in Kerala during the era of Prophet Muhammad (PBUH) after Hindu and Buddhists accepted Islam after interacting with newly Muslim Arab traders.
Later when Raja Dahir looted Muslim ships and kidnapped women then the Caliph sent Muhammad Bin Qasim to Sindh. Raja Dahir lost the battle after which Balochistan, Sindh and Multan become part of Abbasid Caliphate.
Later many other battles were fought and Muslim rule was established but no one enforced religion forcefully as Hindus still live in Balochistan and Kerala the first areas from where Islam spread.
Scholars also played vital role in spreading Islam, many Hindus accepted Islam to be get complete rights of Islam unlike Hindu cast system which degraded lower casts.