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Yangtse basin. The national Chinese state of Sung therefore tried hard to defend Hsiang-yang against the invading Mongol forces, and the town was besieged for five consecutive years (1268-1273). The engineers who built catapults for the Mongols came from Baghdad and had such unmistakably Muslim names as Ala-ud-din and Ismail. This disproves the story told by Marco Polo, that it was the Polos who distinguished themselves by constructing the artillery used against the fortifications of Hsiang-yang10. Another technological field in which Muslim engineers excelled was hydraulic engineering. In Yunnan, a Chinese province that was incorporated into the Chinese-Mongol empire as late as 1253, the governor was a Muslim from, it seems, Turkistan, by the name of Sayyid Ajall Shams-al-Din. He did much for the irrigation of the K'un-ming basin, works that still survive today.11 The eternal hydraulic problem of China, the Yellow River, came, at some time under the Yüan, equally under the supervision of a foreigner; a Persian or rather Arab called Shams (1278-1351). He is the author of a treatise on river conservancy, the Ho-fang 'ung-i "Comprehensive Explanation of River Conservancy", published in 1321. The grandfather of Shams had come to China in the wake of the Mongol conquest of Arabia and settled there. Apart from hydraulic engineering, Shams is described in his biography as having been an expert in astronomy, geography, mathematics, and musical or rather acoustic theory. He had not yet lost the cultural ties with the homelands of his forefathers, as so many other Westerners did once they had come to China, but was still interested in what the Chinese biography called "books of foreign nations". In this case, Arab or Persian literature is certainly meant. But, ironically, the biography of Shams has been incorporated in the section reserved for Confucian Learning in the Yüan dynastic history! It is a matter for regret that of all the works he wrote in his lifetime, only the treatise on Yellow River conservancy has survived. The list of the books he wrote is tantalizing to read because their titles reflect a lasting interest in Western (Islamic) scientific thought, and their contents would perhaps have enabled us to see more clearly the interplay of Chinese and Near Eastern science.12
The largest group of foreigners in Yüan China were, however, not the Arab and Persian or Syrian scientists but merchants from the Near East. Transcontinental trade flourished under the Mon-