The great Ma'rib Dam in South Arabia…

It is not known when An Lushan's son An Renzhi was born, although he was said to be not yet twenty when Emperor Xuanzong gave him the mostly honorary title of minister of vassal affairs, likely in 751.

He is An Lushan's second son, and his mother is An Lushan's first wife Lady Kang.

At some point, Emperor Xuanzong had given him the name of Qingxu.

The first definitive historical references to him were in 752, when, in a defeat that An Lushan suffered against the Xi, An Lushan was said to have fallen into a hole and was only saved through the effort of An Qingxu and others.

Also that year, when An Lushan's close associate Ji Wen went to meet An Lushan before departing for the Tang capital Chang'an, it was An Qingxu that An Lushan sent to accompany Ji to the borders of his territory.

When An Lushan rebelled at his post at Fanyang Circuit (headquartered in modern Beijing) in 755, An Qingxu was apparently with his father and accompanied his father south.

In response to An Lushan's rebellion, An Qingxu's mother Lady Kang and older brother An Qingzong, then at Chang'an, were executed, and after An Lushan captures Chenliu Prefecture (roughly modern Kaifeng, Henan), it is An Qingxu who realizes that An Qingzong had been executed and who tearfully informs his father, sending his father into a rage in which he executes the Tang soldiers who had surrendered to him at Chenliu.

An Lushan declares himself Emperor at Luoyang on Lunar New Year's day, 756 (February 5), establishing a new state of Yan, making Zhang Tongru and the surrendered Tang official Daxi Xun his chancellors.

He creates An Qingxu the Prince of Jin and another son, An Qinghe, the Prince of Zheng.

Meanwhile, Yan Zhenqing's cousin Yan Gaoqing who initially submits to An, rises against An at Changshan Prefecture (roughly modern Baoding, Hebei) but is quickly defeated and delivered to An in Luoyang; An executes him.

An also sends An Qingxu to make a preliminary assault on …

…the Tong Pass, located in the east of the Central Plain, north of the Qin Mountains, south of Wei and Luo River, east of the Mount Hua and in between the three provinces of Shanxi, Shaanxi and Henan.

The pass is defended by the Tang general Geshu Han, who repels An Qingxu's attack.

The Tang army, led by Zhang Xun, successfully defends their fortress against the rebels in the Battle of Yongqiu.

An Lushan’s army advances on Chang’an, the imperial capital, but T'ang forces check their advance for six months, after An Lushan's forces advance through the Tongguan pass toward the city.

The Emperor Xuanzong flees the capital for Sichuan.

During Emperor Xuanzong's flight, his soldiers are provoked to kill his chancellor Yang Guozhong and compel him to execute his consort Yang Guifei.

An Lushan also has other members of the Emperor's family killed.

Emperor Suzong of Tang ascends to the throne on August 12, 656, after his father Emperor Xuanzong abdicates.

Yan forces have captured Chang'an by early 757 and forced both Emperor Xuanzong and his crown prince Li Heng to flee.

It is said that An Lushan was having eye problems and had become blind, and was also suffering from ulcers on his body.

As a result, his temper has become terrible, and his servants, if they have caused him any ill will, are often whipped or caned, and sometimes even executed.

Having declared imperial title, he spends most of his time inside the Luoyang palace, and his generals rarely see him, with most important matters going through his official Yan Zhuang,—but even Yan and a favorite eunuch of An's, Li Zhu'er, are being frequently battered.

Meanwhile, An Lushan favors another son An Qing'en, the son of his second wife Lady Duan (who might have carried the title of empress by this point).

An considers naming An Qing'en as his crown prince, instead of An Qingxu, who is otherwise considered to have received this honor.

An Qingxu often fears that An Lushan will put him to death.

He, Yan, and Li Zhu'er therefore plot.

On the night of January 29, 757, with Yan and An Qingxu watching outside, Li Zhu'er takes a sword into the palace and attacks An Lushan; An Lushan tries to fight back, but cannot locate a sword that he had put under his bed, and LI Zhu'er kills him.

The next morning, Yan first announces to the Yan officials that An Lushan is seriously ill and is creating An Qingxu crown prince.

An Qingxu then takes the throne before announcing An Lushan's death.

An Qingxu, now emperor of Yan, orders his general Yin Ziqi to besiege Suiyang (in modern day Shangqiu, Henan).

Yin Ziqi joins with Yang Chaozong before the siege, with a total army size over one hundred and thirty thousand men.

The governor of Suiyang, Xu Yuan, had heard of Zhang Xun's fortress defense abilities in the Battle of Yongqiu and asks him for help.

Zhang Xun knows that if Suiyang falls, the rest of Tang's territory south of the Yangtze River will be threatened.

He agrees to help immediately.

The united army of Zhang Xun and Xu Yuan, around seven thousand men, prepares to defend Suiyang with their lives.

Xu Yuan focuses on supplies management and after-battle repairs.

Zhang Xun, on the other hand, focuses on battle tactics.

The Tang soldiers never let up despite daily sieges by the Yan army.

Zhang Xun's troops play the war-drums during the night, acting as if they are going to fight (a tactic that army apparently had used before).

Consequently, the Yan army is forced to stand on guard during the night, and suffers from the lack of sleep.

Eventually, some troops do not bother to put on their armor when they hear these battle drums, and continue sleeping.

After the Yan army lowers their defenses, Zhang Xun's forces ambush them very successfully.

Zhang Xun has long wanted to give the Yan morale a major blow, and the best way to do this is to hurt or kill the Yan general Yin Ziqi.

Zhang orders his troops to shoot weeds, instead of arrows, at a few enemy soldiers.

When these soldiers notice that they are being shot by weeds, they are overjoyed, and promptly run to Yin Ziqi to report that the Tang army has already run out of arrows.

Zhang Xun notices where the soldiers run and orders his best archers to shoot at Yin Ziqi.

One such arrow hits Yin Ziqi in his left eye, throwing the Yan army instantly into chaos.

The siege ends with this expected major blow to the Yan morale.

After sixteen days of siege and ambush, Yan has already lost twenty thousand men.

Yin Ziqi decides that his army is too tired to fight, so he orders a temporary retreat to regroup.

Yin Ziqi returns to besiege Suiyang two months later, with an additional twenty thousand fresh troops.