The Tausug appear to have come to Sulu from northeastern Mindanao as a result of contact with Sama-Bajau traders. This movement probably began in early Sung times and was related to the growth of Chinese trade during the Sung ( A.D. 960-1279) and Yuan ( A.D. 1280-1368) periods. Linguistic evidence suggests that a Tausug-speaking community may have originated from a bilingual population established in Jolo by Sama traders and their Tausug-speaking wives and children between the tenth and eleventh centuries. By the end of the thirteenth century the Tausug emerged in the islands as a regionally powerful commercial elite. The date of earliest Islamic penetration is uncertain, but initial contact possibly began in late Sung times, when Arab merchants opened direct trading links with southern China by way of the Sulu Archipelago. There also seems to have been some early proselytizing by Chinese Muslims. Islam was later reinvigorated in Sulu by Sufi missionaries, who came from Arabia or Iraq via Malaya and Sumatra. The Sulu sultanate was established in the mid-fifteenth century, putatively by the legendary Salip (Sharif) Abu Bakkar or Sultan Shariful Hashim. Its establishment consolidated the ascendancy of the Tausug and appears to have furthered their social and economic differentiation from the Sama-Bajau-speaking Samal. The sultanate reached the height of its power in the eighteenth and early nineteenth centuries, when its influence extended from Sulu through the coastal foreshores of Mindanao and northern Borneo. Jolo emerged as a major center of trade and piracy and as an entrepôt for slaves, most of them taken in the Christian Philippines. Slavery made possible an intensification of trade-related production and, in addition to being practiced by Tausug slavers, was carried out by Ilanon and Balangingi Samal under the commission of Tausug aristocrats. Following Spain's colonization of the Philippines in the sixteenth century, warfare with the Spanish was almost continuous for the next 300 years. The first Spanish attack on Jolo town occurred in 1578. The town was occupied briefly in the seventeenth century and a permanent garrison was established for the first time in 1876. After Spain's defeat in the Spanish-American War, American troops occupied Jolo town in 1899, but stiff resistance prevented them from gaining control over the interior of the island until 1913. The Pax Americana that followed saw the abolition of slavery, confiscation of firearms, and temporary curtailment of piracy and feuding. In 1915, under the terms of the Carpenter Agreement, Sultan Jamal ul-Kiram II relinquished all claims to secular power, while retaining his religious role as an Islamic sovereign. Since World War II indigenous forms of armed conflict have revived. Sulu today is a major center of Islamic separatism, the birthplace of many of the founding leaders of the present Moro National Liberation Front, and the site of some of the most destructive fighting of the recent past.