The term adivasis is not one that travels much beyond India's borders. Used to describe the indigenous peoples who inhabited the Indus Valley thousands of years before waves of Aryan, Afghan and Mughal invaders swept in, 85m Indians are today classified as belonging to these "scheduled tribes".
Of those, the majority live in a hilly forest belt that traverses several states across southern and eastern India. Many speak mutually unintelligible languages of which there is often no written form. Chhattisgarh, one of those states, was the scene this week of a bloody ambush in which Maoist guerrillas - known in India as Naxalites after a 1967 peasant uprising in the West Bengali village of Naxalbari - gunned down 76 police officers in the fastness of the jungle.
The attack was the worst so far in a rumbling guerrilla war that last year alone robbed more than 1,100 people of their lives. Atrocities have been committed by guerrillas and government forces alike. Manmohan Singh, India's softly-spoken prime minister and a man not normally prone to unnecessary flights of rhetoric, has called the Naxalite uprising the most potent internal threat to India's national security.