It is speculated that the Toraja migrated to Sulawesi from Indochina some 4,000 years ago. There is evidence of relations with the coastal Buginese and Luwunese as early as the sixteenth century. By the late nineteenth century, trade between Toraja highlanders and Muslim lowlanders intensified: coffee and slaves were exported in return for guns, salt, and textiles. Toraja traditionally resided in autonomous and at times mutually hostile mountain villages. It was not until the arrival of the Dutch colonial forces in 1906 that the Toraja were united under a single political authority. By 1913 missionaries from the Calvinist Reformed Church had arrived, precipitating dramatic sociocultural changes. Scholars suggest that the activities of these Protestant missionaries stimulated a unifying sense of Toraja identity. The region was occupied by the Japanese during World War II. Following that war, in 1949, the region was declared a part of the new nation of Indonesia. Today, Tana Toraja Regency has become a major tourist destination (in 1988 179,948 tourists visited the area).