During the reign of Ming Taizu, Zhu Yuanzhang, he enfeoffed his sons and grandsons as vassal kings across the realm, which led to their growing power and posed a serious threat to the central imperial authority. After Emperor Jianwen ascended the throne, he took measures to address this issue by steadily reducing the power of the vassal kings, sparking their intense resentment. Zhu Di, the Prince of Yan stationed in Beiping, unwilling to wait idly for his demise, led his army southward to campaign against Emperor Jianwen. In the end, Zhu Di replaced Emperor Jianwen to become the third emperor of the Ming Dynasty. This is the historically famous "Jingnan Campaign."
During Zhu Yuanzhang's reign, while vigorously strengthening centralized power, he also greatly enhanced the imperial family's strength to ensure the Ming Dynasty could endure for countless generations. Zhu Yuanzhang enfeoffed his twenty-four sons and one grandson as princely lords, stationing them at military strongholds across the country. His original intention was for these princely lords to safeguard the Ming Dynasty's rule, but the expansion of their power inevitably posed a serious threat to central authority. Scholar Ye Boju once submitted a memorial pointing this out, but unfortunately it failed to attract Zhu Yuanzhang's attention.
After Zhu Yuanzhang's death, his grandson Zhu Yunwen ascended the throne, historically known as Emperor Minghui, though later generations customarily refer to him by his reign title as Emperor Jianwen. Emperor Jianwen was the second son of Crown Prince Zhu Biao; at the very beginning of the Ming Dynasty's establishment, Zhu Biao was appointed crown prince by his father Zhu Yuanzhang. Zhu Yuanzhang believed that it was precisely because the Yuan Dynasty rulers had failed to appoint a crown prince early on that court coups frequently occurred, and he did not want the Ming Dynasty to repeat the same mistake.
Unfortunately, Zhu Biao died young at the age of thirty-seven. When deciding on the new crown prince, Zhu Yuanzhang did not consider his many other sons but instead turned his attention to Zhu Biao's second son, Zhu Yunwen—Zhu Biao's eldest son had died in infancy. At just fifteen years old, Zhu Yunwen was upright, gentle in temperament, and filial to his elders, which deeply pleased his grandfather Zhu Yuanzhang. However, compared to his uncles, the young Zhu Yunwen's meager experience was clearly insufficient to support his ascension to the throne. Yet Zhu Yuanzhang did not care about this and insisted on appointing this grandson as the crown prince.
This move by Zhu Yuanzhang sparked discontent among many feudal princes, especially Yan Prince Zhu Di, who was eligible to inherit the throne. In the early days of the Ming Dynasty, when Zhu Yuanzhang first appointed the crown prince, he had considered Zhu Di. Zhu Di was brave and resourceful, far surpassing his mediocre elder brother Zhu Biao, but because he was not the eldest son, he missed out on the throne. For an ambitious man like Zhu Di, it is easy to imagine how unwilling he felt. Since he could not passively wait for the throne to fall into his hands, he had to actively pursue it. Thus, it can be said that Emperor Jianwen's policy of reducing the power of feudal princes actually provided Zhu Di with the perfect opportunity to fight for the throne.
Shortly after Emperor Jianwen ascended the throne, the conflict between the emperor and the feudal princes finally came to light. At that time, with the support of his ministers Qi Tai and Huang Zicheng, Emperor Jianwen first declared war on the princes by ordering the reduction of their territories. Several weaker princes were the first to fall victim: the princes of Zhou, Dai, Min, Xiang, and Qi were successively stripped of their power. Among all the princes, the Prince of Xiang suffered the most tragic fate, ultimately burning himself to death. The Prince of Yan, Zhu Di, was the most powerful among the princes. Since Emperor Jianwen adopted a strategy of tackling the easier targets first in the process of reducing the princes' power, Zhu Di's position became increasingly precarious as the campaign progressed.
Zhu Di was the fourth son of Zhu Yuanzhang; when Zhu Di was born, Zhu Yuanzhang was engaged in a fierce battle with Chen Youliang at Taiping and didn't even have time to name his son. It wasn't until just before the establishment of the Ming Dynasty that Zhu Yuanzhang finally named him Zhu Di, by which time Zhu Di was already seven years old. As a child, Zhu Di suffered greatly from the hardships of war and was even sent by his father to live in his hometown for a period, giving him a deep understanding of the suffering of the common people. From a young age, Zhu Di was exceptionally intelligent and brave; at eleven, he was enfeoffed as the Prince of Yan, and at twenty-one, he was ordered to lead troops and garrison Beiping. After Zhu Di replaced his nephew, Emperor Jianwen, and ascended the throne, in order to quell criticism from the world, he claimed that his birth mother was Empress Ma, but in reality, his birth mother was merely one of Zhu Yuanzhang's concubines.
Zhu Di had been stationed in Beiping for many years, during which various Mongol tribes repeatedly harassed the city, but Zhu Di, relying on his extraordinary military talent, drove them back time and again. Over these years in Beiping, Zhu Di's power steadily grew, and he eventually became the most powerful feudal prince.
During the process of reducing the power of the feudal princes, Emperor Jianwen paid the most attention to Zhu Di. He ordered people to secretly monitor Zhu Di, ready to arrest him at any time. Unwilling to wait for his doom, Zhu Di first killed the officials sent by Emperor Jianwen to spy on him, then used the pretext of punishing Qi Tai and Huang Zicheng, the two "treacherous ministers" who advocated for the reduction of princely power, to raise an army and march south. Zhu Di called this action the "Jingnan Campaign," meaning to suppress the rebellion instigated by Qi Tai and Huang Zicheng. The Yan army led by Zhu Di quickly captured Beiping, Tongzhou, Jizhou, Huairou, and other areas.
When the news arrived, Emperor Jianwen was greatly alarmed and hastily dispatched General Geng Bingwen to lead a 300,000-strong army to suppress the Yan forces. In the subsequent direct confrontations with the Yan army, the Ming troops under Geng Bingwen suffered repeated defeats. Consequently, Emperor Jianwen then sent Li Jinglong to command a 500,000-strong army northward to attack Beiping.
During this period, Zhu Di led an elite force of Yan troops to capture Daning. Taking advantage of the situation, Li Jinglong launched a fierce assault on Beiping but was unable to breach its defenses. After Zhu Di returned in triumph, he decisively routed the Ming army commanded by Li Jinglong.
The following year, Li Jinglong was defeated again in the Battle of Baigou River. Zhu Di pursued his advantage and attempted to capture Jinan, but Tie Xuan, who was defending the city, held it firmly, and the Yan army could not break through no matter what they tried, eventually being forced to withdraw. Tie Xuan's reputation soared as a result, and he soon replaced Li Jinglong's position, leading troops to campaign against the Yan army. In the subsequent battles, Zhu Di was once again defeated by Tie Xuan.
Zhu Di was not discouraged; the following year, he once again led his troops southward and achieved consecutive victories. A year later, Zhu Di shifted the battlefield from the north to the south, vowing to capture the then-capital, Nanjing.
A few months later, the Yan army breached Yangzhou and other areas, bringing Nanjing to a critical moment of survival. Emperor Jianwen, in great anxiety, had to send Zhu Di's cousin, Princess Qingcheng, to negotiate peace with him. Princess Qingcheng appealed to emotion and reason, urging Zhu Di to withdraw his troops. However, Zhu Di's mind was made up—how could a few words from his cousin sway him?
Princess Qingcheng returned in disappointment. A month later, the Yan army crossed the Yangtze River and breached Nanjing. As the city fell, a great fire broke out in the imperial palace, and Emperor Jianwen died by setting himself ablaze. In the end, Zhu Di could only see a charred corpse beyond recognition, and no one could tell whether it was truly Emperor Jianwen. One theory holds that Emperor Jianwen had already escaped the palace and become a Buddhist monk.
To determine whether Emperor Jianwen was alive or dead, after ascending the throne, Zhu Di sent his minister Hu Ying to travel across the country in search of Jianwen's whereabouts. It is said that Zhu Di also dispatched Zheng He on his voyages to the Western Seas for the same purpose. As for the final outcome of the investigation, historical records provide no clear account. However, based on various historical sources, later generations speculate that Emperor Jianwen likely became a Buddhist monk, as he had seen through the illusions of the mortal world and had no desire to reclaim the throne, so Zhu Di did not pursue him to the death.
After the "Jingnan Campaign" ended, Zhu Di ascended the throne as emperor, historically known as Emperor Chengzu of the Ming Dynasty. Subsequently, Zhu Di exterminated the entire clans of over fifty ministers, including Qi Tai and Huang Zicheng, and continued implementing policies to reduce the power of feudal princes, thereby strengthening central authority.