Yanyun Sixteen Prefectures refers to the sixteen prefectures centered on Youzhou and Yunzhou, which is equivalent to the current Beijing and the northern part of Tianjin, northern Hebei, and northern Shanxi. During the Five Dynasties and Ten Kingdoms period, Youyun Sixteen Prefectures were ceded to the Khitan by Shi Jingyao, the founding emperor of the Later Jin Dynasty, and several dynasties in the Central Plains did not fully recover the region until the end of the Yuan Dynasty, when Zhu Yuanzhang's rebel army captured the capital of the Yuan Dynasty, Dadu, and completely recaptured the Sixteen Prefectures of Yanyun.
The Five Dynasties and Ten Kingdoms were a period of chaos, and since Zhu Wen established himself, he had fallen into chaos. And this Shi Jingyao was originally a subordinate of Emperor Mingzong of Later Tang, Li Siyuan, or his son-in-law. In the process of the establishment of the Later Tang Dynasty, he made great contributions. However, after Li Siyuan's death, Later Tang fell into turmoil, and the emperor also distrusted him, and Shi Jingyao, who supported the army and respected himself, became more and more ambitious, so he turned to the Khitan and, as an envoy of Hedong Jiedu, he gave you the Sixteen Prefectures of Youyun to the Khitan and recognized him as a thief.
Since then, Youyun Sixteen Prefectures have been in the hands of the Liao people. In fact, in the late Five Dynasties and Ten Kingdoms period, Chai Rong of later Zhou once went on a northern expedition, and although he made some gains, he could only end up with his death.
Zhao Kuangyin later took his place and established the Northern Song Dynasty. During the Zhao Kuangyin period, the main target was the separatist regime in the south. But he also knew the key to Youyun Sixteen Prefectures, after all, without this barrier, the capital of the Northern Song Dynasty, Kaifeng, was almost directly facing the Khitan Iron Horse, which was very dangerous.
At that time, Zhao Kuangyin planned to redeem it with money, but this was impossible.
During the reign of his brother Zhao Guangyi, he also had two Northern Expeditions, the target of which was Youyun Sixteen Prefectures, but it still ended in failure.
Since then, the Song and Liao wars have also continued, but basically become the Liao people's attack, the Northern Song Resistance is just nonsense, and it is even more nonsense to recover youyun Sixteen Prefectures, and it is fortunate to be able to defend the existing territory.
After the rise of the Jin people, after the agreement with the Northern Song Dynasty to jointly destroy the Liao, the Jin returned the Sixteen Prefectures of Song Yanyun, but who believed was stupid. You must know that the Northern Song Dynasty was destroyed by the Jin people. The Southern Song Dynasty was again felt by the Jin Dynasty, and it was even more impossible to recover the lost land.
After that, the Mongols came, Kublai Khan unified the world and established the Yuan Dynasty, and during this period there was no need to recover or not. After all, the Yuan Dynasty was a unified dynasty.
In the last year of the Yuan Dynasty, the peasant revolt broke out, zhu Yuanzhang rose up in it, and he was the only one who laid the foundation for the Northern Expedition. Zhu Yuanzhang drove out the Mongols through the Northern Expedition and captured the Capital of Yuan.
But objectively speaking, the purpose of Zhu Yuanzhang's Northern Expedition was not for the sixteen prefectures of Youyun, and he probably did not know the story of Shi Jingyao at all, his purpose was to fight the world and drive out the Mongols.