1. Destroying the Northern Han Dynasty was a key step to realize the policy of unification in the early Song Dynasty.
Zhao Kuangyin successfully ascended the throne through the mutiny in Chen Qiao. While he inherited the post-Zhou Shizong throne, he also inherited the political legacy of the post-Zhou Shizong era and devoted himself to the great cause of national reunification.
In the end, Song Taizu and Zhao Kuangyin formulated a unified strategy of "easy first, difficult later, south first and north first". He also pacified the southern countries according to this strategy.
In the end, only the Northern Han Dynasty in the north and the sixteen states of Youyun occupied by Liao were left.
Song Taizong's personal expedition to the Northern Han Dynasty after he succeeded to the throne was precisely to carry out the established unification strategy and complete the great cause of reunification expected by the Northern Song Dynasty.
Moreover, after Song Taizong destroyed the Northern Han Dynasty, it immediately took advantage of the situation to attack the Liao State, with the intention of recovering the sixteen states of Youyun, which was also a part of the unified strategy.
Second, Song Taizong hopes to consolidate the throne with great achievements. Please ask his brother's shadow.
Song Taizong inherited his brother Song Taizu's throne through "the sound of candles and axes", which is full of criticism. At least his nephew and brother are potential threats to him.
Pingtan Lake in Song Taizu, the destruction of Houshu, the annexation of Southern Han Dynasty and the destruction of Southern Tang Dynasty were outstanding in the martial arts of ancient emperors.
Song Taizong doesn't want to live in the shadow of his brother.
Song Taizong urgently needs a merit to get rid of the fact that he is inferior to his brother militarily, and also needs such a merit to show that his succession is destiny.
He urgently needs to prove himself with actions, or he urgently needs to surpass his brother and prove that his succession is correct.
Finally, in February (979) of the fourth year of Taiping and Xingguo, Song Taizong and Zhao Guangyi led an army to make personal expedition to destroy the Northern Han Dynasty.
This feat ended the nearly 90-year scuffle between the vassal regions since the end of the Tang Dynasty, and formally unified the whole country, which was enough for him to show off to Song Taizu in the ancestral temple.
However, after the Northern Han Dynasty was destroyed, Song Taizong was not satisfied. Regardless of the opposition of all, he decided to destroy the Northern Han Dynasty, northern expedition to Khitan, and recover sixteen states of Youyun.
This was the dream of everyone in the Central Plains at that time. If successful, it will be an immortal achievement and will fully prove that his succession is extremely correct.
Unfortunately, the northern expedition failed, and he finally fled south by donkey cart.
The second Northern Expedition still failed. In the end, the sixteen states of Youyun were abandoned, and the ethnic policy of the Northern Song Dynasty became "keeping the inner space and outer space", and the pioneering spirit of the Northern Song Dynasty was lost.