An Lushan, originally a general in the Tang dynasty, proclaimed himself emperor and established the short-lived state of Yan in the mid-8th century. His actions were precipitated by mounting frustrations with the Tang court, which he viewed as corrupt and ineffective. An Lushan leveraged his military prowess and the support of disaffected soldiers to launch a rebellion against the Tang dynasty, drawing upon regional alliances and significant military resources.

With his declaration, An Lushan captured the capital city of Chang'an, which symbolized a pivotal moment in the rebellion leading to significant territorial changes across northern China. His establishment of the Yan state lasted for a brief period, characterized by both consolidation of power and internal strife. While he sought to create a new order, the conflict escalated into a broader civil war that engulfed the region, prompting fierce battles between rival factions and prolonged suffering for the populace.

As An Lushan's military campaigns progressed, his regime became marked by tyranny, and his ambition ultimately led to his assassination by his own son. The repercussions of his reign and the subsequent rebellion contributed to the weakening of the Tang dynasty, signifying the beginning of a tumultuous era, often referred to as the Period of Disunion in Chinese history.