As mentioned last time, the Anxi Jiedu, who retreated to Tongguan, made Feng Changqing and Gao Xianzhi take a defensive position and stick to Tongguan. However, because Tang Xuanzong listened to the false accusations of the eunuch Bian Lingcheng of the prison army, he beheaded Chang Qing and Gao Xianzhi for the crime of "losing his discipline". On the first day of the first month of the fifteenth year of Tianbao (756), An Lushan called Emperor Dayan in Luoyang and changed his name to Yuan Shengwu.

After Tang Xuanzong killed the generals Feng Changqing and Gao Xianzhi, he used the sick and abandoned Longyou Jiedu to make Ge Shuhan the deputy marshal of the soldiers and horses, and ordered him to lead an army of 200,000 to guard Tongguan. The terrain of Tongguan is dangerous, easy to defend and difficult to attack. After Geshuhan entered Tongguan, he immediately strengthened the city defense, deep ditches and high fortifications, and closed the retreat. In the first month of the fifteenth year of Tianbao (756), An Lushan ordered his son An Qingxu to lead his troops to attack Tongguan, but was repelled by Ge Shuhan. The main force of the An'an army was blocked at Tongguan for several months and could not advance westward. Seeing that the strong attack could not be carried out, An Lushan ordered Cui Qianyou to camp the old, weak, sick and disabled soldiers in Shaanxi County (west of present-day Sanmenxia City, Henan), and concealed the elite troops, trying to lure Ge Shuhan to abandon the danger and go into battle. In May, Tang Xuanzong received information that the rebel general Cui Qianyou had "less than 4,000 soldiers in Shaanxi County, and all of them were weak and unprepared", so he sent Ling Ge Shuhan to send troops to recover Shaanluo. Ge Shuhan immediately wrote to Tang Xuanzong, he believed: "An Lushan has been accustomed to using troops for a long time, and now he will rebel, he will not be unprepared, he must use the weak soldiers of the division to lure us, if he enters the army, it is just the right plan." Moreover, the rebels are on an expedition, and the benefits are fast. The officers and soldiers relied on the natural danger of Tongguan to resist them, and the advantage was to hold on. Moreover, the rebels were tyrannical, lost the hearts of the people, and were declining, and soon civil strife would break out, and they would be able to capture him without a fight. At the same time, Guo Ziyi and Li Guangbi attacked the rebel general Shi Siming in Hebei, fought several big victories, and the progress was very smooth, so the two of them also thought that Tongguan should only be defended, not lightly, and the two advocated leading the Shuo army to the north to take Fanyang, overthrowing the rebels' lair, and promoting the internal collapse of the rebels. However, Prime Minister Yang Guozhong suspected that Ge Shuhan intended to seek himself, so he told Tang Xuanzong that Ge Shuhan would miss the opportunity if he did not move. Xuanzong once again believed slanderous rumors, ignored the good plans of Guo Ziyi and Li Guangbi, and successively sent Chinese envoys to urge Ge Shuhan to fight. Ge Shuhan was forced to be helpless, knowing that there was no return, but the emperor's order was difficult to disobey, and the history book "Zizhi Tongjian" described Ge Shuhan as "soothing and crying".

Ge Shuhan was forced to lead his troops out of the customs on the fourth day of the sixth month, and on the seventh day of the first month, he met Cui Qianyou's department in Lingbao Xiyuan. Lingbao is bordered by mountains in the south, the Yellow River in the north, and a narrow mountain road 70 miles long in the middle. Cui Qianyou ambushed the elite soldiers on the southern mountain in advance, and led the troops to a decisive battle with the Tang army on the eighth day of the first month. The Tang army led 50,000 elite soldiers led by Wang Sili and others, followed by 100,000 troops led by Pang Zhong and others, and sent another 30,000 people to beat drums and assist on the high ground on the north bank of the Yellow River. The two armies intersected, and the Tang army saw that the rebels were in disarray and wanted to flee, so they drove straight forward, but were lured into the pass. The rebels rose up in ambush and threw rolling wooden stones from the mountain, and the Tang soldiers crowded the pass, which was difficult to spread, and there were many dead and wounded. Goshuhan hurriedly ordered the felt cart to charge in front of him, trying to open a path, but was blocked by the rebels with arson grass carts. The Tang army was dazzled by the smoke and could not see the target clearly, thinking that the rebels were in the thick smoke, so they fired crossbow arrows indiscriminately, and did not know the plan until the sunset. At this time, Cui Qianyou ordered to ride with Luo Jingcai from the southern valley back to the back of the official army to kill, the Tang army was attacked before and after, chaotic, some abandoned their armor and fled into the valley, some were squeezed into the Yellow River and drowned, the cry of despair was shocking, a tragic situation. Seeing the defeat of the former army, the Tang Hou army collapsed without a fight. The Tang army on the north bank of the Yellow River saw that the situation was unfavorable and also dispersed. Ge Shuhan only took hundreds of horsemen to flee in embarrassment, crossed from the Yellow River to the west into Tongguan, and dug three trenches outside Tongguan, all of which were two zhang wide and one zhang deep, and the people and horses fell into the ditch, and it was filled in a while, and the people behind stepped on the corpses. The Tang army had nearly 200,000 troops, and only more than 8,000 fled back to Tongguan. On the ninth day of the first month, Cui Qianyou captured Tongguan. Ge Shuhan withdrew to the Guanxi Station and posted a post to recruit the lost soldiers, wanting to continue to guard Tongguan. The Tibetan general Huoba Guiren surrounded the post station with more than 100 cavalry, went in and said to Ge Shuhan: "The thieves are coming, please get on the marshal." Ge Shuhan walked out of the post station and got on his horse, and Huo Ba Guiren and the generals kowtowed and said: "The marshal has 200,000 soldiers and horses, and he abandoned them all in one battle, how can he have the face to see the Son of Heaven again? And didn't the marshal see what happened to Gao Xianzhi and Feng Changqing?

This battle was a typical example of ambush warfare in the history of Chinese warfare, in which Cui Qianyou lured the Tang army to abandon danger and go into battle; during the battle, he lured the Tang army into the ambush area with his banner in order to escape, thus winning a great victory.

There was no shortage of experienced generals in the Tang Dynasty, but Tang Xuanzong's series of "divine operations" made the counterinsurgency war take a sharp turn. Tang Xuanzong misjudged the situation, refused to adopt the policy of guarding the dangerous points, persisting in exhausting the enemy, and waiting for an opportunity to attack, and prematurely went out of the pass to counterattack, resulting in the loss of both men and land. When the Anshi Rebellion broke out, An Lushan commanded the main rebel army to attack Luoyang and Tongguan, intending to break through these two important towns and take Chang'an directly! Later, Luoyang fell, but because of the strong stubbornness of Gao Xianzhi and Feng Changqing, the Anshi rebels could not attack for a long time, and even forced the enemy to have the intention of retreating.

However, in his later years, Tang Xuanzong Li Longji had already fainted and lost his wisdom and decisiveness when he was young. Gao Xianzhi and Feng Changqing adopted the correct method of warfare, so that the enemy army from afar could not succeed in their plan to fight a quick battle, and Tongguan, as a barrier to Chang'an, also effectively protected Chang'an; however, some treacherous villains spoke ill of Gao Xianzhi and Feng Changqing in front of Li Longji, slandering them for colluding with the Anshi rebels, so they did not engage the rebels head-on for a long time, and Li Longji beheaded the two without careful investigation, causing the imperial court to lose two experienced and brave generals!

Later, Tang Xuanzong sent the elderly Ge Shuhan to lead the army of Tongguan to resist the enemy, and there were 200,000 troops guarding Tongguan at that time! Ge Shuhan correctly judged the situation on both sides, and also believed that holding on to it was the best way to resist the enemy, as the days dragged on, Tang Xuanzong also lost patience with them, and the traitorous minister Yang Guozhong was instigating Tang Xuanzong to issue a holy decree to force Ge Shuhan to fight, Ge Shuhan knew that the battle would be defeated after receiving the holy decree, but he was afraid of the majesty of the imperial power, he had to lead his troops to fight, and in the end he was defeated, and he was also tied to the enemy camp by his subordinates.

Chang'an, the capital of Tang Xuanzong, was in chaos after learning that Tongguan was lost, because Tongguan was the gateway to Chang'an, Tongguan was lost, Chang'an had no danger to defend, and the rebels could drive straight into the Guanzhong Plain and approach Chang'an. On the first day, there were only one or two people in the court, and the emperor went to the Qinzheng Building to issue a book (the book is what the emperor said, the so-called "words of the Son of Heaven are systematic, and the book contains his words." He said that he wanted to recruit himself, but everyone did not believe it. On this day, the emperor's forbidden army honor guard quietly moved to Daming Palace. In the evening, Chen Xuanli, the general of Longwu, reorganized the six armies, rewarded more money, and selected 900 horses from the stables, but the people outside the palace knew nothing about this. Seeing that the Anshi army was approaching day by day, and at dawn on the second day, the emperor fled with his concubine sisters, princes, grandsons, princesses, concubines, Yang Guozhong, Wei Jiansu, Wei Fangjin, Chen Xuanli and close attendants from Yanqiumen. When passing through the Zuozang Treasury (ancient treasury), Yang Guozhong wanted to destroy these treasures to prevent the thieves from getting them, Tang Xuanzong said: "The thieves will loot the people if they can't get the treasures, so it's better to leave them to the thieves." ”

Then Tang Xuanzong fled from Chang'an in embarrassment, and the team marched to Maweipo, and the soldiers of the Sixth Army finally couldn't bear it anymore and launched a mutiny to kill the traitorous minister Yang Guozhong and others, and then Gao Lishi and others hanged Yang Guifei. Soon after, the crown prince Li Heng ascended the throne in Lingwu, Gansu, and honored Tang Xuanzong as the emperor. Tang Xuanzong Li Longji was quite helpless after learning all this, after all, he was not willing to abdicate, but he was helpless, at this time he had lost his heart and became a loner, so he had to accept it.

In June of the fifteenth year of Tianbao (756), An Lushan occupied Chang'an.