Sixteen Prefectures in the context of Youzhou (ancient China)

The Liao dynasty (/ljaʊ/; Khitan: Mos Jælud; traditional Chinese: 遼朝; simplified Chinese: 辽朝; pinyin: Liáo cháo), also known as the Khitan State (Mos diau-d kitai huldʒi gur), officially the Great Liao (Chinese: 大遼; pinyin: Dà Liáo), was a Khitan-led imperial dynasty of China and empire ruled by the Yelü clan that existed between 916 and 1125. Founded around the time of the collapse of the Tang dynasty, at its greatest extent it ruled over Northeast China, the Mongolian Plateau, the northern part of the Korean Peninsula, southern portions of Siberia, and the northern tip of the North China Plain.

The dynasty rose from the consolidation of power among the Khitans in the 8th century and their expansionist campaigns in the latter half of the 9th century. Eventually the Yila chieftain, Abaoji, became the leader of the Khitans and proclaimed a Chinese-style dynastic state in 916. The Liao dynasty launched multiple military campaigns against neighboring states and peoples including the Kumo Xi, Shiwei, Tatars, Zubu, Khongirad, Balhae, Goryeo, Later Tang, and the Song dynasty. Its conquests include the Sixteen Prefectures (including present-day Beijing and part of Hebei) by fueling a proxy war that led to the collapse of the Later Tang (923–936). In 1004, the Liao launched an expedition against the Northern Song dynasty. After heavy fighting and large casualties between the two empires, both sides worked out the Chanyuan Treaty. Through the treaty, the Liao forced the Northern Song to recognize them as peers and heralded an era of peace and stability between the two powers that lasted approximately 120 years. It was the first state to control all of Manchuria.

The Jin–Song Wars were a series of conflicts between the Jurchen-led Jin dynasty (1115–1234) and the Han-led Song dynasty (960–1279). In 1115, Jurchen tribes rebelled against their overlords, the Khitan-led Liao dynasty (916–1125), and declared the formation of the Jin. Allying with the Song against their common enemy the Liao dynasty, the Jin promised to cede to the Song the Sixteen Prefectures that had fallen under Liao control since 938. The Song agreed but the Jin's quick defeat of the Liao combined with Song military failures made the Jin reluctant to cede territory. After a series of negotiations that embittered both sides, the Jurchens attacked the Song in 1125, dispatching one army to Taiyuan and the other to Bianjing (modern Kaifeng), the Song capital.

Surprised by news of an invasion, Song general Tong Guan retreated from Taiyuan, which was besieged and later captured. As the second Jin army approached the capital, Song emperor Huizong abdicated and fled south. Qinzong, his eldest son, was enthroned. The Jin dynasty laid siege to Kaifeng in 1126, but Qinzong negotiated their retreat from the capital by agreeing to a large annual indemnity. Qinzong reneged on the deal and ordered Song forces to defend the prefectures instead of fortifying the capital. The Jin resumed war and again besieged Kaifeng in 1127. They captured Qinzong, many members of the imperial family and high officials of the Song imperial court in an event known as the Jingkang Incident. This separated north and south China between Jin and Song. Remnants of the Song imperial family retreated to southern China and, after brief stays in several temporary capitals, eventually relocated to Lin'an (modern Hangzhou). The retreat divided the dynasty into two distinct periods, Northern Song and Southern Song.

Jicheng, less commonly called Ji and Yanjing, was an ancient city in northern China, which has become the longest continuously inhabited section of modern Beijing. It has been known by numerous other names over its long history, usually in reference to the changing territories it presided over. Historical mention of Ji dates to the founding of the Zhou dynasty in about 1045 BC. Archaeological finds in southwestern Beijing where Ji was believed to be located date to the Spring and Autumn period (771–476 BC). The city of Ji served as the capital of the ancient states of Ji and Yan until the unification of China by the Qin dynasty in 221 BC. Thereafter, the city was a prefectural capital for Youzhou through the Han dynasty, Three Kingdoms, Western Jin dynasty, Sixteen Kingdoms, Northern Dynasties, and Sui dynasty. With the creation of a Ji Prefecture in present-day Tianjin during the Tang dynasty, the city of Ji became more exclusively referenced as Youzhou or by its subsequent renamings including Yanjing. Youzhou was one of the Sixteen Prefectures ceded to the Khitans during the Five Dynasties. The city then became the southern capital of the Liao dynasty and then the main capital of the Jurchen Jin dynasty. In the 13th century, Kublai Khan built a new capital city for the Yuan dynasty adjacent to Ji to the north. The old city of Ji became a suburb to Khanbaliq/Dadu, whose site was developed under the Ming and Qing dynasties into modern Beijing.

The Alliance Conducted at Sea (Chinese: 海上之盟) was a political alliance in Chinese history between the Song and Jin dynasties in the early 12th century against the Khitan-led Liao dynasty. The alliance was negotiated from 1115 to 1123 by envoys who crossed the Bohai Sea. Under the alliance, the two nations agreed to jointly invade the Liao, split captured territories, and cede the Sixteen Prefectures to the Song, and forswore making unilateral peace with the Liao. In 1121–23, the Song faltered in their military campaigns, but the Jin succeeded in driving remnants of the Liao imperial court to Central Asia where they formed the Western Liao dynasty. The Jin handed over several of the Sixteen Prefectures to the Song including modern-day Beijing. In 1125, the alliance ended when the Jin, sensing Song weakness, invaded southward and eventually captured the Song capital of Kaifeng in 1127.

Nanjing was the name for modern Beijing during the Khitan-led Liao dynasty of China, during which it served as the empire's southern capital. To distinguish "Nanjing" (literally 'southern capital') from the modern city of Nanjing in Jiangsu, and Beijing Damingfu, the name for modern Daming County in Hebei Province during the Northern Song dynasty, Chinese historians sometimes refer to Liao-era Beijing as Liao Nanjing (辽南京; 遼南京). The Liao acquired the city, then known as Youzhou, in the cession of the Sixteen Prefectures in 938 by the Later Jin, one of the five short-lived dynasties that ruled northern China following the end of the Tang dynasty. The city was officially renamed "Nanjing, Youdu Fu" (南京幽都府). In 1012, the city was renamed "Nanjing, Xijin Fu" (南京析津府). The city was also colloquially referred to at the time as "Yanjing". In 1122, the city was captured by the Jurchen-led Jin dynasty (1115–1234)—who officially renamed it "Yanjing", ending the use of "Nanjing" for what is today modern Beijing.

Yunzhou or Yun Prefecture (Chinese: 雲州) was a zhou (prefecture) in imperial China seated in modern Datong, Shanxi, China. It existed (intermittently) from 640 to 1044.

It was one of the Sixteen Prefectures.