Flows and frictions in mobile spaces connecting South and East Asia occupy spatial histories in monsoon environments that span the arid northern steppe and the humid southern tropical seas. Many centuries of migration, trade, travel, and settlement along routes across the Hindu Kush, up and down the Indo-Ganga Basins, and around Indian Ocean coastal regions produced expanding cultural spaces, where mobile warriors and local elites formed strategic alliances and power relations that turned social space into political territory. Patronage for religious rituals, elites, and knowledge served to sanctify these power relations. Religion thus became a territorial technology, and its powers of social boundary-making became more strident during the mid-twentieth-century shift from more fluidly inclusive imperial territory to more rigidly exclusionary nation-state territorialism.