In 710 AD, Emperor Zhongzong of Tang Li Dan was made emperor by his son and sister, and his eldest son Li Chengqi cried and said, "Crown Prince is the main position of the country. When the world is peaceful, he should first be the eldest son. When the world is uneasy, he should first make a meritorious person. My son asked not to make me the crown prince for death."

Li Chengqi , the eldest son of Li Dan and Empress Liu. In the first year of Diaolu (679), Empress Liu, who was the prime minister at that time, gave birth to Li Chengqi in Chang'an. Li Chengqi was named the Prince of Yongping by his grandfather Emperor Gaozong of Tang.
was awarded the title of crown prince at the age of six, and his mother's body was not preserved. In 684 AD, Li Xian, the Emperor Zhongzong of Tang, who had inherited the throne for less than two months, made a wild statement that he wanted to grant his father-in-law the prime minister. Wu Zetian, who was in charge of the government, pulled Li Xian down from the throne, abolished him as King of Luling, changed Li Dan to the emperor, and made Li Chengqi and his son the crown prince and queen.

However, although Li Dan was the emperor, he had the name of the emperor but no reality. Not only was he allowed to inquire about the government affairs, his whole family was also imprisoned by Wu Zetian in the bedroom and was not allowed to enter and exit at will. The scope of his activities was only the bedroom.
That's it. After Li Dan became emperor for six years, he was given to Wu Zetian. His identity was demoted to the emperor's heir. In order to survive, he also requested to change to the surname Wu. Li Chengqi was demoted to the emperor's grandson and was driven out of Luoyang with his brothers to the fiefdom. , but his mother was not so lucky.

In 693 AD, Wu Zetian's favorite maid Wei Tuaner was rejected by temptation of Li Dan. In anger, she pointed her finger at the mother of Dou Defei, the mother of Empress Liu and Li Dan's third son Li Longji, and falsely accused the two of them of cursing Wu Zetian with witchcraft.
As a result, Wu Zetian secretly executed Empress Liu and Concubine Dou De from Li Dan, and their bodies were gone. Li Dan was afraid of his mother and dared not ask about the disappearance of his two wives, and acted as if nothing had happened.

lived for two years, and falsely accused the maid of the household and concubine Dou De, and killed the queen of Wu, and killed him in the palace. The burial secret is unknown - "New Book of Tang: Biography of Concubines"
witnessed the palace change and refused to accept the prince
In 698 AD, after much thought, Wu Zetian gave up the plan to establish a nephew and took Li Xian, who had been under house arrest for 15 years, and Li Dan took the initiative to give up the position of the prince to his brother.
Although Li Xian regained the identity of the prince, Wu Zetian was not at ease with him and handed over the government to the brothers Zhang Yizhi and Zhang Changzong. During this period, Li Xian's eldest son Li Chongrun and his daughter Princess Yongtai were executed by Wu Zetian for privately discussing Zhang Yizhi's brothers.

In 705 AD, with the help of Zhang Jianzhi and others, Li Xian mutiny, killed Zhang Yizhi's brothers, and forced Wu Zetian to abdicate. After the restoration, Li Xian won the title of Li Chengqi as King Cai, with a fief of 400 households, totaling 700 with the original one, but Li Chengqi refused to accept it and said: "My ministers have no talent and cannot afford the fief of a great country." ”
The brother Gu mutiny and deposed the emperor and established his father, crying and let the prince
In 710 AD, Empress Wei and his daughter poisoned Li Xian to death. Princess Taiping and Shangguan Wan'er issued a will to make Li Xian's son Li Chongmao the crown prince. Empress Wei was the empress dowager in the court and took charge of the government, and her brother Li Dan was the Taiwei's assistant. However, Empress Wei wanted to imitate her mother-in-law Wu Zetian, and she gave up Li Dan's power to assist in the government, and planned to kill Li Dan and Princess Taiping.

Li Longji learned about this and joined forces with Princess Taiping to kill Empress Wei and her accomplices, forcing Li Chongmao to abdicate to Li Dan.
And on the day Li Longji's mutiny was successfully told Li Dan, the father and son cried bitterly. Li Dan named Li Longji as King Ping, the prime minister and commanded the imperial guards to the left and right military power, and Li Chengqi was appointed King Song and General of the Left Guard. He said to Li Longji: "The disaster of the Tang Dynasty is that you are stable, and the people rely on your strength!"
After Li Dan was restored, he discussed with his ministers to establish a crown prince, one of whom was the eldest son and the other had the contribution to pacifying Wei family, so it was difficult to decide. Li Chengqi thought that the four princes, Li Jiancheng, Li Chengqi, Li Xian and Li Chongjun, were deposed and killed, so he cried and gave way and said: "When the world is peaceful, you should first establish the eldest son, and when the world is uneasy, you should first establish the person who has made meritorious first. My son asked not to make me the prince for death.”

At this time, the ministers involved in the killing of Wei also supported the establishment of Li Longji as the crown prince, and jointly submitted a memorial saying: "Ping Wang has the contribution to pacifying the world. I also heard that princes below the level of talent have a desire to give in. Your Majesty should make King Ping the crown prince to meet the wishes of the subjects of the highest and lowest. ”
So, Li Dan followed the advice of his ministers and made Li Longji the crown prince. In order to make up for Li Chengqi, he added 2,000 households to make up for Li Chengqi.
brother Gu fought, but his family was killed
In 712 AD, Li Dan passed the throne to Li Longji in advance on the grounds of passing the throne to avoid disaster, but he still controlled the government affairs, and the battle between Princess Taiping and Li Longji became more and more powerful.

relied on Li Dan's trust, and five of the seven prime ministers came from her disciples. More than half of the civil and military ministers were willing to submit to her, but they were still one step away and could not fight Li Longji.
In 713 AD, Li Longji took the initiative to kill Princess Taiping's accomplices on the grounds of Princess Taiping's rebellion, and sentenced Princess Taiping and his whole family to death. Even Princess Taiping's aunt brothers were not spared. Only the second son Xue Chongjian was spared.
was favored by his brother, humiliated his reputation, and ended up being rich and honored. After Princess Taiping's death, Li Dan issued an edict to return the government to Li Longji, and Li Chengqi knew his younger brother's power well, so he never again Inquire about the government affairs, he recites poems with his friends every day. In order not to be suspicious, he stole the wife of the cake seller. In order to avoid the title of Concubine Dou De, he took the initiative to change his name to Li Xian.
However, Li Longji is very good to his brothers. Every time Li Chengqi celebrates his birthday, he personally goes to congratulate him. Only when the delicacies he pays for tribute are delicious, he sends someone to give him a serving of Li Chengqi.

In 742 AD, Li Chengqi died at the age of 63. Li Longji issued an edict to posthumously named him Let the emperor and the princess be the queen. It rained heavily on the day when the burial was buried. He personally carried the spirit and sent his son Li Tan to walk in the mud for more than ten miles.
Li Chengqi, as the eldest son, judged the reason and knew how to take the initiative to retreat to the position of the prince. Not only did he save his life, but he also gained the trust of his younger brother. After his death, he was posthumously named the emperor. This is a rare wise man who is wise and stupid.
References:
"Old Book of Tang"
"New Book of Tang"
"Zizhi Tongjian"