An Lushan in the context of "Yang Guozhong"

The An Lushan rebellion was a civil war in China that lasted from 755 to 763, at the approximate midpoint of the Tang dynasty (618–907). It began as a commandery rebellion attempting to overthrow and replace the Tang government with the rogue Yan dynasty. The rebels succeeded in capturing the imperial capital Chang'an after the emperor had fled to Sichuan, but eventually succumbed to internal divisions and counterattacks by the Tang and their allies. The rebellion spanned the reigns of three Tang emperors: Xuanzong, Suzong, and Daizong.

On 16 December 755, An Lushan, the jiedushi of the Taiyuan Commandery, mobilized his army and marched to Fanyang. An Lushan led the rebellion for two years before he was assassinated by his son An Qingxu. Two years after An Qingxu's ascension, Shi Siming, the governor of Pinglu Commandery and a close ally of An Lushan, killed An Qingxu and usurped the leadership. Shi Siming ruled for two years, but was in turn killed by his own son Shi Chaoyi, who ruled for another two years until the Yan dynasty fell to Tang forces on 17 February 763. There were also other anti-Tang rebel forces, especially those in An Lushan's base area in Hebei, as well as Sogdian forces and other opportunist parties who took advantages of the chaos.

Yan (Chinese: 燕; pinyin: Yān), also known as the Great Yan (Chinese: 大燕; pinyin: Dà Yān), was a dynastic state of China established in 756 by the former Tang general An Lushan, after he rebelled against Emperor Xuanzong of Tang in 755. The state collapsed in 763 with the death of An Lushan's former subordinate Shi Chaoyi (son of Shi Siming), who was the last person to claim the title as emperor of Yan.

Emperor Xuanzong of Tang ([ɕwǎn.tsʊ́ŋ]; 8 September 685 – 3 May 762), personal name Li Longji, was an emperor of the Tang dynasty of China, reigning from 712 to 756. His reign of 44 years was the longest during the Tang dynasty. Through two palace coups, he seized the throne and inherited an empire still in its golden age. He was initially assisted by capable chancellors like Yao Chong, Song Jing and Zhang Yue who were already serving as government officials before Xuanzong ascended the throne. However, under Emperor Xuanzong, the empire reached its turning point and went into sharp decline and near collapse, due to numerous political missteps throughout his long reign, such as over-trusting chancellors Li Linfu, Yang Guozhong and general An Lushan, with Tang's golden age ending in the An Lushan rebellion.

The jiedushi or jiedu was a regional military governor in imperial China. The title was established in the Tang dynasty and abolished in the Yuan dynasty. The post of jiedushi has been translated as "military commissioner" or "governor", "legate", and "regional commander". Originally introduced in AD 711 to counter external threats, the jiedushi were posts authorized with the supervision of a defense command often encompassing several prefectures, the ability to maintain their own armies, collect taxes and promote and appoint subordinates.

Powerful jiedushi warlords eventually became fanzhen rulers, able to override the power of the central government of Tang. An early example of this was An Lushan, who was appointed jiedushi of three regions, which he used to start the An Lushan Rebellion that abruptly ended the golden age of the Tang dynasty. Even after the difficult suppression of that rebellion, some jiedushi such as the Three Fanzhen of Hebei were allowed to retain their powers due to the weakened state of the court. The jiedushi were one of the primary factors which contributed to the political division of the Five Dynasties and Ten Kingdoms period, a period marked by continuous infighting among rival kingdoms, dynasties, and regional regimes established by the jiedushi.

An Qingxu (安慶緒) (730s – 10 April 759), né An Renzhi (安仁執), was a son of An Lushan, a general of the Chinese Tang dynasty who rebelled and took the imperial title, and then established his own state of Yan. An Qingxu served as the Prince of Jin in 756–757, and later killed his father and took the imperial title for himself. He was eventually defeated by Tang forces and cornered at Yecheng in present-day Hebei. After An Lushan's general Shi Siming lifted the siege, An Qingxu met Shi to thank him, but Shi arrested and executed him.

Shi Siming (Chinese: 史思明) (19th day of the 1st month, 703? – 18 April 761), or Shi Sugan (史窣干), was a Chinese military general, monarch, and politician during the Tang dynasty who followed his childhood friend An Lushan in rebelling against Tang, and who later succeeded An Lushan's son An Qingxu as emperor of the Yan state that An Lushan established.

Li Linfu (Chinese: 李林甫; pinyin: Lǐ Línfǔ) (died January 3, 753), nickname Genu (Chinese: 哥奴), formally the Duke of Jin (Chinese: 晉公), was a Chinese historian, musician, and politician during the Tang dynasty, serving as a chancellor for 18 years (734–752), during the reign of Emperor Xuanzong—one of the longest terms of service for a chancellor in Tang history, and the longest during Xuanzong's reign.

Li was known for his flattery of the Emperor and skill in the political scene, which enabled him to remain powerful throughout his lengthy duration as chancellor. His treachery in cutting off all routes for all potential political challengers, including false accusations against other officials and the granting of key military commands to non-Han commanders, were blamed for the deterioration of Emperor Xuanzong's reign, which culminated in the An-Shi Rebellion after Li Linfu's death. Xuanzong himself admitted after the An Lushan Rebellion broke out (when Li had died) that Li was most adept at removing political rivals and being jealous of any potential challengers, a factor which resulted in the Tang administration lacking seriously competent officials during the Tianbao era.