Jia Dan

Jia Dan (, 730 – 805), courtesy name Dunshi and formally Duke Yuanjing of Wei , was a Chinese cartographer, military general, and politician from Cangzhou, Hebei during the Tang dynasty.

Background Jia Dan was born in 730, during the reign of Emperor Xuanzong. His family was from Cang Prefecture (滄州, in modern Cangzhou, Hebei) and traced its ancestry to the Han dynasty official Jia Yi, through officials of Cao Wei, Jin dynasty (266–420), Liu Song, Southern Qi, Liang dynasty, Northern Qi, Northern Zhou, Sui dynasty, and Tang dynasty. Both his grandfather Jia Zhiyi and father Jia Yuanyan served as county-level officials.

Career

Early career During Emperor Xuanzong's Tianbao era (742–756), Jia Dan passed the imperial examinations and was made the sheriff of Linqing County (, in modern Liaocheng, Shandong). After he submitted suggestions on the matters of the times to Emperor Xuanzong, he was moved to be the sheriff of Zhengping County (, in modern Yuncheng, Shanxi) — closer to the capital Chang'an, and therefore considered a promotion despite it being the same level of office. While serving under Wang, Jia was promoted to be the deputy mayor of Taiyuan Municipality and deputy military governor. He later served as the prefect of Fen Prefecture (汾州, in modern Linfen, Shanxi) for seven years and was known for ruling the prefecture well. As the minister of vassal affairs, he would have met with foreign envoys in order to acquire information about their native countries. Historian Edward Schafer states that it is no doubt that Jia's remarkable knowledge of foreign geography was derived from these interviews with foreign delegates and diplomats.

In 784, while Emperor Dezong was at Liang Prefecture after he fled there due to rebellions by the general Zhu Ci and Li Huaiguang, there was an occasion when Jia sent his officer Fan Ze to make reports to Emperor Dezong. After Fan's return, there was suddenly an imperial edict issued making Fan the military governor of Shannan East Circuit and recalling Jia to Emperor Dezong's location to serve as the minister of public works (, Gongbu Shangshu). When the edict arrived, Jia was hosting a feast, and he received the edict as if nothing had happened. After the feast was over, he informed Fan of his promotion and immediately began the transition, including having the other officers greet Fan as their new superior. The officer Zhang Xianfu was angered, believing that Fan had treacherously seized Jia's position, and he wanted to kill Fan. Jia stopped him, pointing out that because Fan had imperial sanction, he was the proper military governor. That same day, he left his post and headed for the emperor's location, taking Zhang with him to avoid any further disturbance. Jia was soon made the defender of the eastern capital Luoyang.

In 793, Jia was recalled to Chang'an to serve as You Pushe , one of the heads of the executive bureau of government (尚書省, Shangshu Sheng). He was also given the designation Tong Zhongshu Menxia Pingzhangshi , making him a chancellor, serving with Lu Zhi (Tang dynasty), Zhao Jing, and Lu Mai.

In 800, when Lu Qun the military governor of Yicheng died, Jia Dan advocated that Emperor Dezong commission a military governor without first consulting the officers of the circuit, believing that such consultation showed weakness. Emperor Dezong agreed and directly made the official Li Yuansu the military governor of Yicheng. In 801, Jia completed a 40-volume work that included a large map of the Chinese and the non-Chinese populations, and descriptions of the various circuits of Tang as well as foreign nations (see further below). Emperor Dezong awarded him with a number of silk and silver items, as well as a horse, and created him the Duke of Wei. The map depicted China and other countries including its former colonies in Central Asia that were lost to the Uyghurs and Tibetans. Huanghua Sida Ji was presented to Emperor Dezong of Tang in 798, while both the 40-volume book and the map were presented to the emperor in 801.

In the 40-volume work that Jia completed in 801, Jia wrote of two common sea trade routes in his day: one from the coast of the Bohai Sea towards Silla in Korea and another from Guangzhou through Malacca towards the Nicobar Islands, Sri Lanka and India, the eastern and northern shores of the Arabian Sea to the Euphrates River. Jia's book contains some of the most accurate accounts of the Arab world in Tang Chinese sources. He wrote that the ships in the Euphrates had to anchor at the mouth of the Euphrates and transfer the trade goods on land towards the capital (Baghdad) of Dashi Guo (Abbasid). A small branch of this extensive second trade route led all the way to Dar es Salaam in Tanzania, East Africa. Confirming Jia's reports about lighthouses in the Persian Gulf, Arabic writers a century after Jia wrote of the same structures, writers such as al-Mas'udi and al-Muqaddasi.