Why is Nanjing called one of the Three Wus? What does one of the three Wu mean?

The theory of "three Wu" is not the equivalent concept of horizontal arrangement, but the result of vertical development and evolution. Therefore, with the continuous division of administrative regions, people in different times will form different concepts of "three Wu" in their minds. Up to now, there are about eight different "three Wu" statements:

First, take Wu Jun, Xing Wu and Huiji counties as the "Three Wu". This was formed in Wu Dong during the Three Kingdoms period. In Li Daoyuan's Notes on Water Classics, "(Huiji) is divided into three parts, and the world number is three Wu:,, Huiji."

Second: Take Wu Jun, Xing Wu and Danyang as the "Three Wu". In the Eastern Jin and Southern Dynasties, Nanjing, the capital including Jiangning, Dantu, Danyang, Runzhou, Jurong and Wuhu, was more important, forming Danyang County with Nanjing as the center, Xing Wu County with Huzhou as the center and Wujun County with Suzhou as the center, while Huiji County was far south of Qiantang River, which naturally alienated at that time, forming the "New Three Wus".

Thirdly, taking Wu Jun, Xing Wu and Yixing as the "Three Wus", they were recorded in Li Jifu's Records of Yuanhe Counties and Liang Zaiyan's Records of Ten Roads and Four Fans in the Tang Dynasty. Yixing county is separated from the county, and the county is separated from Wuxian county, which is a trinity.

Fourth: Jinling is the middle Wu, Ezhou is the south Wu, and Wuchang is the lower Wu. According to Wu Shuo, it was translated from Tong Ji written by Nalan Xingde in Tang Dynasty to Wu Di Ji written by Lu Guangwei, but some people have never seen the original text when consulting the Tongzhi Edition of Wu Di Ji. Wuchang in Ezhou is a different name, which may be due to personal memory.

Fifth: Take Suzhou, Changzhou and Huzhou as the "Three Wu". The article "Ci Hai San Wu" quotes: "In Song Dynasty, the tax authorities set up a geographical map of the past dynasties, with Suzhou, Changzhou and Shanghai as the three Wu." Suzhou is the seat of Wuxian County, Changzhou is the seat of Piling County, and Huzhou is the seat of Xing Wu County. During the Jin Dynasty, Piling County included the area from Wuxi to Dantu, which was equivalent to Danyang County mentioned earlier.

Sixthly, Suzhou, Runzhou and Huzhou are regarded as "Three Wu", and Runzhou is governed by Danyang County, which is the same as Article 2, but the expression is different.

Seventh: Suzhou is Wu Dong, Runzhou is Zhongwu, and Huzhou is Xiwu. Same as above.

Eighth: Take Danyang, Changzhou and Suzhou as the three Wu. This may be due to the combination of Danyang County, Piling County and Wu Jun County.

What you see, including Nanjing, is probably the second and fourth, and the second is more likely.