The failure of the Northern Song Dynasty to seize the sixteen states of Yanyun by force was mainly due to the following reasons: First, it lacked adequate preparation. After destroying the Northern Han Dynasty, Song Taizong hastily launched a war against Liao without rest and detailed planning, and the army was tired

The failure of the Northern Song Dynasty to seize the sixteen states of Yanyun by force was mainly due to the following reasons:

One is the lack of adequate preparation. After destroying the Northern Han Dynasty, Song Taizong hastily launched a war against Liao without rest and detailed planning, and the army was exhausted and the strategic deployment was imperfect.

Second, the generals made mistakes in command. For example, in the Battle of the Gaoliang River, there were problems with the tactical arrangement of the Song army, and after achieving certain results, the enemy advanced lightly, resulting in a counterattack by the Liao army.

The third is the issue of the army's combat effectiveness. The Northern Song Dynasty practiced a policy of emphasizing literature over military force, and paid relatively little attention to military construction, and there was a certain gap between the fighting quality and fighting will of the army and that of the Liao army.

Fourth, the Liao army is relatively strong. The military strength of the Liao Dynasty at that time should not be underestimated, and it attached great importance to the sixteen states of Yanyun and resisted desperately.

Fifth, logistical supply difficulties. Long-distance expeditions and long supply lines are prone to problems such as untimely supply, which affects the army's operations.

Sixth, internal contradictions. There were different opinions and differences within the Northern Song Dynasty on military operations, which also affected the determination to fight and the coordination and unity of action.