The world famous historian, Will Durant has written in his Story of Civilisation that "the Mohammedan conquest of India was probably the bloodiest story in history".
India before the advent of Islamic imperialism was not exactly a zone of peace. There were plenty of wars fought by Hindu princes. But in all their wars, the Hindus had observed some time-honoured conventions sanctioned by the Sastras. The Brahmins and the Bhikshus were never molested. The cows were never killed. The temples were never touched. The chastity of women was never violated. The non-combatants were never killed or captured. A human habitation was never attacked unless it was a fort. The civil population was never plundered. War booty was an unknown item in the calculations of conquerors. The martial classes who clashed, mostly in open spaces, had a code of honor. Sacrifice of honor for victory or material gain was deemed as worse than death.
Islamic imperialism came with a different code--the Sunnah of the Prophet. It required its warriors to fall upon the helpless civil population after a decisive victory had been won on the battlefield. It required them to sack and burn down villages and towns after the defenders had died fighting or had fled. The cows, the Brahmins, and the Bhikshus invited their special attention in mass murders of non-combatants. The temples and monasteries were their special targets in an orgy of pillage and arson. Those whom they did not kill, they captured and sold as slaves. The magnitude of the booty looted even from the bodies of the dead, was a measure of the success of a military mission. And they did all this as mujahids (holy warriors) and ghazls (kafir-killers) in the service of Allah and his Last Prophet.