Why did Zhu Di build the Forbidden City?
The reason why Zhu Di built the Forbidden City was to consolidate his political power.
Zhu Di wrote to his father Zhu Yuanzhang in the early days of establishing the Ming Empire. The strategic location of Beiping City and the geography of the capital were actually very conducive to the Ming Empire. However, these were dismissed by Zhu Yuanzhang, who still chose In fact, because of Zhu Di's existence, Mongolia and the Jurchens have been unable to form an alliance or form an effective invasion.
So during the Jingnan period, when Zhu Di ascended the throne, the first thing he did was to build the capital into Peiping. First, the emperor guarded the country, and second, he made clear the impact of Peiping's geographical location on the nomadic people outside the Great Wall. Very far-reaching, because the emperor was in Beiping City, all the elite troops of the Ming Empire were hoarded in Beiping. Therefore, the cavalry of the Ming Empire in subsequent dynasties were very powerful, and many of them were truly elite troops.
Extended information:
When Zhu Di was just beginning to plan to move the capital to Beijing, his wife Queen Xu passed away. The mausoleum should be built in Nanjing, but Zhu Di secretly sent a minister and a Feng Shui master to Beijing to find Ji Yang to build the mausoleum.
Two years later, a place more than 20 miles north of Changping was designated by Zhu Di as a forbidden area in the mausoleum area. This is today's Ming Tombs. By using the death of Queen Xu to build the mausoleum, the ministers all realized that this was a signal from the emperor to move the capital.
After this, some ministers in Nanjing began to speak out and directly opposed Emperor Yongle's hidden intention of moving the capital. And they were all demoted. Later, ministers all strongly demanded that the first capital of the Ming Dynasty be set in Beijing. Zhu Di's long-cherished desire to move the capital finally came true. Later historians believe that this decision meant that China's political center began to move northward, and China's geopolitics changed from then on.