The original home of the Santals is believed to have been the Champa Kingdom of northern Cambodia, which explains their affinities with the Mon-Khmer groups. Physical anthropologists usually classify them under the Austro-Mongoloid type. They probably entered India well before the Aryan invasions and came by way of Assam and Bengal, as their traditions indicate. They assume the existence of a Santal kingdom, a tradition which is supported by the collections of medieval Santal weapons at the Oslo Ethnographic Museum and by the remains of what may be identified as Santal hill forts from the medieval period. Little else is known of this kingdom to which Santal mythic traditions allude. Moreover, the mythic tradition recalls a war between the Santals and a part-Hindu prince, Mandho Singh, who was born of a Santal mother. Mandho Singh succeeded in recruiting followers among the Santals who followed him to the south of Nagpur, settled there, and became more Hinduized. Early contacts with the British led to the Santal rebellion of 1854-1856, in which some ten thousand Santals were killed. They became an important source of plantation labor, while missionary efforts introduced writing and had some influence on their culture. Only small numbers were actually converted to Christianity. Today, the Santals are among the main sources of support for the Jharkhand "tribalist" movement, in which they collaborate to some extent with other Mundari-speaking groups.