In history, the battle that led to General Xue being directly demoted as a civilian was the Battle of Dafeichuan. Dafeichuan was originally a campaign to suppress the Tubo uprising in the Tang Dynasty. At that time, General Xue led 200,000 troops to attack Tubo, and Xue's deputy Guo was under Xue's command for a long time. He felt that he could replace Xue one day, so he deliberately delayed the delivery of food and grass in this war. In the process of delaying the delivery of food and grass, he was suddenly attacked by the Tubo army and Xue's army.
After the war, Xue was held accountable as commander-in-chief, bearing in mind his previous achievements, and did not execute him. However, the war also led to a sharp rise in the strength of Tubo, even equal to that of the Tang Dynasty at that time, which was intolerable to the Tang Dynasty at that time. Therefore, in the following years, the Tang Dynasty continued to fight Tubo, but the effect was not ideal.
Have to say, Xue was able to save a life, is indeed a blessing in disguise. You know, his defeat at that time cast a shadow over the history of the Tang Dynasty. Although he is not directly responsible for the failure of this war, he should be put to death as a leader.