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Van Praag states that the Ming court established diplomatic delegations with Tibet merely to secure urgently needed horses. Wang and Nyima argue that these were not diplomatic delegations at all, that Tibetan areas were ruled by the Ming since Tibetan leaders were granted positions as Ming officials, that horses were collected from Tibet as a mandatory "corvee" tax, and therefore Tibetans were "undertaking domestic affairs, not foreign diplomacy". Sperling writes that the Ming simultaneously bought horses in the Kham region while fighting Tibetan tribes in Amdo and receiving Tibetan embassies in Nanjing. He also argues that the embassies of Tibetan lamas visiting the Ming court were for the most part efforts to promote commercial transactions between the lamas' large, wealthy entourage and Ming Chinese merchants and officials. Kolmas writes that while the Ming maintained a laissez-faire policy towards Tibet and limited the numbers of the Tibetan retinues, the Tibetans sought to maintain a tributary relationship with the Ming because imperial patronage provided them with wealth and power. Laird writes that Tibetans eagerly sought Ming court invitations since the gifts the Tibetans received for bringing tribute were much greater in value than the latter. As for the Yongle Emperor's gifts to his Tibetan and Nepalese vassals such as silver wares, Buddha relics, utensils for Buddhist temples and religious ceremonies, and gowns and robes for monks, Tsai writes "in his effort to draw neighboring states to the Ming orbit so that he could bask in glory, the Yongle Emperor was quite willing to pay a small price". The Information Office of the State Council of the PRC lists the Tibetan tribute items as oxen, horses, camels, sheep, fur products, medical herbs, Tibetan incenses, thangkas (painted scrolls), and handicrafts; while the Ming awarded Tibetan tribute-bearers an equal value of gold, silver, satin and brocade, bolts of cloth, grains, and tea leaves. Silk workshops during the Ming also catered specifically to the Tibetan market with silk clothes and furnishings featuring Tibetan Buddhist iconography.

Wang and Nyima believed horses were collected from Tibet as what kind of tax?
a mandatory "corvee" tax