The Chinese dynastic histories of the "Old Book of Tang" and "New Book of Tang" mention (拂菻), which they equated with Daqin (the Roman Empire). These are recorded as having begun in the year 643 with an embassy sent by the king "Boduoli" (波多力, Constans II Pogonatos) to Emperor Taizong of Tang, bearing gifts such as red glass and green gemstones. Other contacts are reported taking place in 667, 701, and perhaps 719, sometimes through Central Asian intermediaries. These histories also record that the Arabs ("Da shi" 大食) sent their commander "Mo-yi" (Chinese: 摩拽伐之, Pinyin: "Mó zhuāi fá zhī"), to besiege the Byzantine capital, Constantinople, and forced the Byzantines to pay them tribute. This Arab commander "Mo-yi" was identified by historian Friedrich Hirth as Muawiyah I (r. 661–680), the governor of Syria before becoming the Umayyad caliph. The same books also described Constantinople in some detail as having massive granite walls and a water clock mounted with a golden statue of man. The Byzantine historian Theophylact Simocatta, writing during the reign of Heraclius (r. 610–641), relayed information about China's geography, its capital city "Khubdan" (Old Turkic: "Khumdan", i.e. Chang'an), its current ruler "Taisson" whose name meant "Son of God" (Chinese: "Tianzi"), and correctly pointed to its reunification by the Sui Dynasty (581–618) as occurring during the reign of Maurice, noting that China had previously been divided politically along the Yangzi River by two warring nations.