Why was the Forbidden City built?
The Forbidden City had been the very political center and the seat of power in ancient China since it was built by the Ming Emperor Chengzu Zhu Di (1360-1424). After Zhu Di took the throne from his nephew and enthroned in Nanjing, there were many ministers against him in the court. Therefore, he wanted to move the capital from Nanjing to his former fiefdom Beijing to weaken the power of the ministers who were followers of last emperor and opposed to him. In addition, the northern border was often invaded by nomads at that time, thus he moved the capital northward to Beijing to guard the north.
Emperor Zhu Di wanted to move the capital to his former fief.
Ming Chengzu Zhu Di has deep feelings for Beijing. Although he was born and raised in Nanjing, he had been guarding Beijing for 20 years and had been accustomed to the climate and diet of the North.
When he was 11 years old, he was honored the king of Yan by his father Zhu Yuanzhang (1328-1398), the founder of Ming Dynasty. Beijing was his fief and he had been living there since then. Gradually Beijing became the core area under the jurisdiction of Zhu Di. Before Zhu Di had not become the emperor of the Ming Dynasty, his power range was mostly concentrated in the north, and various military affairs and civil affairs in the north were mostly managed by him. So Beijing was his political base where he and his trusted followers worked together and left a lot of memories in this land, so he never forget this place even if he became the emperor and lived in the royal palace in Nanjing.
A new seat of power can weaken the influence of the last emperor.
Over the years in Beijing, Zhu Di has established a strong influence in the north, especially in Beijing. After taking the throne from his nephew, there are many former ministers who are unwilling to work for him, and even openly confront him. He was even almost killed by a minister who objected to him one day when he was holding his morning court.
In order to get rid of these former ministers who opposed to him and weaken their political power, Zhu Xi made up his mind to move the capital to Beijing to eliminate the influence of these ministers. Nanjing was established to the second capital besides the capital city Beijing.
A political center in the north can better guard the northern frontiers.
Before Zhu Di became the emperor of Ming, he was the King of Yan and guarded the northern frontiers and protected people in Beijing and surrounding areas from being robbed by the nomadic Mongolians. When he took over the throne and moved to Nanjing, the defense in the north was weakened, and the Mongolians harassed the territory of Ming more frequently. In order to strengthen the military power in the north and block the harm caused by the Mongolian power, Zhu Di moved the capital to Beijing, which was also the beginning of the Ming Dynasty’s policy “the Emperor guards the national gate”.