<P> The Hongwu Emperor's grandson, Zhu Yunwen, assumed the throne as the Jianwen Emperor (1398--1402) after the Hongwu Emperor's death in 1398 . In a prelude to a three - year - long civil war beginning in 1399, The Jianwen Emperor became engaged in a political showdown with his uncle Zhu Di, the Prince of Yan . The emperor was aware of the ambitions of his princely uncles, establishing measures to limit their authority . The militant Zhu Di, given charge over the area encompassing Beijing to watch the Mongols on the frontier, was the most feared of these princes . After the Jianwen Emperor arrested many of Zhu Di's associates, Zhu Di plotted a rebellion . Under the guise of rescuing the young Jianwen Emperor from corrupt officials, Zhu Di personally led forces in the revolt; the palace in Nanjing was burned to the ground, along with the Jianwen Emperor, his wife, mother, and courtiers . Zhu Di assumed the throne as the Yongle Emperor (1402--1424); his reign is universally viewed by scholars as a "second founding" of the Ming dynasty since he reversed many of his father's policies . </P> <P> The Yongle Emperor demoted Nanjing as a secondary capital and in 1403 announced the new capital of China was to be at his power base in Beijing . Construction of a new city there lasted from 1407 to 1420, employing hundreds of thousands of workers daily . At the center was the political node of the Imperial City, and at the center of this was the Forbidden City, the palatial residence of the emperor and his family . By 1553, the Outer City was added to the south, which brought the overall size of Beijing to 4 by 41⁄2 miles . </P> <P> After lying dormant and dilapidated for decades, the Grand Canal was restored under the Yongle Emperor's rule from 1411--1415 . The impetus for restoring the canal was to solve the perennial problem of shipping grain north to Beijing . Shipping the annual 4,000,000 shi (one shi is equal to 107 liters) was made difficult with an inefficient system of shipping grain through the East China Sea or by several different inland canals that necessitated the transferring of grain onto several different barge types in the process, including shallow and deep - water barges . William Atwell quotes Ming dynasty sources that state the amount of collected tax grain was actually 30 million shi (93 million bushels), much larger than what Brook notes . The Yongle Emperor commissioned some 165,000 workers to dredge the canal bed in western Shandong and built a series of fifteen canal locks . The reopening of the Grand Canal had implications for Nanjing as well, as it was surpassed by the well - positioned city of Suzhou as the paramount commercial center of China . Despite greater efficiency, there were still factors which the government could not control that limited the transportation of taxed grain; for example, in 1420 a widespread crop failure and poor harvest dramatically reduced the tax grain delivered to the central government . </P> <P> Although the Yongle Emperor ordered episodes of bloody purges like his father--including the execution of Fang Xiaoru, who refused to draft the proclamation of his succession--the emperor had a different attitude about the scholar - officials . He had a selection of texts compiled from the Cheng - Zhu school of Confucianism--or Neo-Confucianism--in order to assist those who studied for the civil service examinations . The Yongle Emperor commissioned two thousand scholars to create a 50 - million - word (22,938 - chapter) long encyclopedia--the Yongle Encyclopedia--from seven thousand books . This surpassed all previous encyclopedias in scope and size, including the 11th - century compilation of the Four Great Books of Song . Yet the scholar - officials were not the only political group that the Yongle Emperor had to cooperate with and appease . Historian Michael Chang points out that the Yongle Emperor was an "emperor on horseback" who often traversed between two capitals like in the Mongol tradition and constantly led expeditions into Mongolia . This was opposed by the Confucian establishment while it served to bolster the importance of eunuchs and military officers whose power depended upon the emperor's favor . </P>

Why did ming rulers repair and expand the grand canal