The Song Dynasty ended the Five Dynasties and Ten Kingdoms, but was unable to capture Youzhou, mainly due to the following reasons:
First of all, the Song army was tired from a long battle and lacked logistics. In the first month of 979, Zhao Guangyi, Taizong of the Song Dynasty, sent 200,000 troops to the Northern Han Dynasty, and in Zhao Guangyi's opinion, it was easy for him to recover the Northern Han Dynasty. But he forgot that his elder brother Zhao Kuangyin failed to attack the Northern Han three times, and even Zhao Kuangyin's old superior, Chai Rong, also attacked the Northern Han, but unfortunately it also ended in failure. When the military operation to attack the Northern Han was not smooth, Song Taizong once again ordered the Song army in the rear to go to reinforcements, and he himself drove the expedition himself. The Song army attacked the Northern Han Dynasty for 4 months, and the soldiers did not want to continue fighting. Because attacking Hebei from Shanxi required crossing heavy mountain ranges, the Song army did not carry too many siege equipment. In the end, the military generals of the Song Dynasty did not make any preparations, did not formulate the corresponding offensive routes and various plans, and did not have time to prepare enough war materials.
Secondly, the strength of the Liao army and the determination of the Liao State were underestimated. In the process of the Song army's attack on the Northern Han Dynasty, the Song army defeated the Liao army that came to reinforce it, and Song Taizong began to despise the Liao army in his heart, thinking that there was still an absolute chance of winning with five to one. But in fact, the Liao State sent 70,000 reinforcements led by famous generals such as Yelu Xiuge and Yelu Xianzhen, all of whom were cavalry and had undergone long-term training.
In the end, the emperor's defeat caused the Song army to lose everything. After the reinforcements of the Liao State arrived in Youzhou, Yelu Xiuge led 30,000 Liao troops to take the initiative to challenge the Song army camp, and Song Taizong also personally went into battle. However, due to his defeat, the morale of the Song army was frustrated, and they finally lost all the games.
To sum up, the Song Dynasty's inability to capture Youzhou was the result of a combination of factors such as exhaustion of the Song army, insufficient logistics, contempt for the Liao army, and the emperor's defeat.