Later Qin

Qin, known in historiography as the Later Qin (384–417) or Yao Qin (姚秦), was a dynastic state of China ruled by the Yao clan of Qiang ethnicity during the Sixteen Kingdoms period in northern China. The Later Qin is entirely distinct from the Qin dynasty, the Former Qin and the Western Qin.

Its second ruler, Yao Xing, supported the propagation of Buddhism by the Madhyamakin monk Kumārajīva.

All rulers of the Later Qin declared themselves emperors, but for a substantial part of Yao Xing's reign, he used the title Heavenly King.

Background
The Yao clan was from Nan’an Commandery (南安郡; southeast of present-day Longxi County, Gansu) and claimed descent from the Shaodang Qiang. Yao Yizhong was chieftain under the Western Jin dynasty, and during the Disaster of Yongjia, he occupied Yumei (榆眉; east of present-day Qianyang County, Shaanxi) and welcomed many refugees under his wing. He later submitted to the Han-Zhao dynasty, and then the Later Zhao dynasty, where he associated himself with the commander, Shi Hu. After Shi Hu seized the government in 333, he followed Yizhong's advice of relocating the powerful Di and Qiang families in the Guanzhong to live around the capital, Xiangguo (襄國, in modern Xingtai, Hebei). Yizhong and his family were relocated to Shetou (灄頭; southeast of present-day Zaoqiang County, Hebei).

Although Yizhong was one of Shi Hu's most trusted officials, he and many other military generals colluded to overthrow his successor, Shi Shi after his death in 349. As Later Zhao descended into civil war, Yizhong tried to return west to the Guanzhong with his army, but was defeated by the Di general, Fu Hong, whose family founded the Former Qin dynasty in 351. Thus, Yizhong remained behind to aid the last emperor, Shi Zhi, in his war against Ran Min.

After Shi Zhi's death in 351, Yizhong advised his sons to move south to join the Eastern Jin dynasty. His son, Yao Xiang succeeded him in 352 and fulfilled his promise. He partook in the early Jin northern expeditions as a general, but due to suspicion from his superior, Yin Hao, he later rebelled in 354. He led his army through northern China in hopes of returning to his ancestral home in Longxi, fighting against Former Qin and Jin forces along the way. However, in 357, he was killed in an ambush by Former Qin forces, prompting his brother, Yao Chang to surrender with their army.

Yao Chang became a general during the reign of Fu Jian and participated in various campaigns, but was not present at the disastrous Battle of Fei River in 383. After the battle, two branches of the Murong-Xianbei rebelled, forming the Later Yan in northeastern China and the Western Yan near Former Qin's capital, Chang'an in 384. Yao Chang initially aided Fu Jian against the Western Yan, but during the course of the war, he feared punishment following a serious defeat and fled to the horse pastures north of the Wei River.

Reign of Yao Chang
At the same time, many of the local Han Chinese and tribal gentry clans had lost faith in the Former Qin and saw Yao Chang as a suitable successor. They gathered thousands of Qiang families and led them to join him. After some hesitation, he agreed to lead their coalition, taking the title of Everlasting King of Qin and proclaiming a new reign era in 384. To distinguish between the two states, historiographers refer to the Fu clan's state as Former Qin and Yao Chang's state as Later Qin.

Initially, Yao Chang avoided going straight for Chang’an, which was hotly contested between Fu Jian and Western Yan forces. He submitted to the stronger Western Yan, and after several battles with Former Qin forces, he ambushed and captured Fu Jian, who left Chang'an with his army in search of food. Yao Chang tried to force Fu Jian into formally abdicating the throne to him, but after he refused, had him killed instead. Chang’an eventually fell to Western Yan forces, who soon left to return to their homeland in the east. In 386, Yao Chang occupied the city, where he elevated himself to Emperor of (Later) Qin.

Despite Fu Jian’s death, there were still pockets of Former Qin and semi-independent forces in the Guanzhong region. A distant cousin of Fu Jian, Fu Deng, was acclaimed the new Emperor of (Former) Qin and waged war against Yao Chang. Yao Chang lost several battles to Fu Deng early on, but brought the conflict to a stalemate with a crucial victory at the Battle of Dajie in 389. From this point on, Fu Deng was unable to launch a major campaign, and Yao Chang soon gained the advantage by subjugating local warlords.

Early reign of Yao Xing and zenith of Later Qin
In 394, Yao Chang died and was succeeded by his son, Yao Xing. Hearing news of Yao Chang's death, Fu Deng led his army to attack Later Qin. At the Battle of Feiqiao, Later Qin won a decisive victory by crushing the main Former Qin force. No longer posing a threat, Yao Xing soon captured and executed Fu Deng, while the last ruler of Former Qin was killed in battle by Western Qin forces in 394. Yao Xing thus unified the Guanzhong, establishing Later Qin as a regional power. While he initially inherited his father's title of Emperor, he changed it to Heavenly King in 399.

Under Yao Xing, the Later Qin greatly expanded their borders, occupying areas in the Ordos, Longxi and Hedong regions. Most notably, in 399, they capitalized on Eastern Jin’s internal turmoil to capture Luoyang and several commanderies north of the Han and Huai rivers. In 400, they conquered Western Qin, and in 401, they forced the Later Liang into submission after besieging their capital. Fearing Later Qin’s presence, the other Hexi states, Southern Liang, Northern Liang and Western Liang, followed suit. Despite success in the west, Yao Xing was dissuaded from expanding east after a heavy defeat to the Northern Wei at the Battle of Chaibi in 402. The Later Liang surrendered their territory in 403, and in 405, Chouchi also submitted, bringing Later Qin to its peak.

Yao Xing upheld Confucianism by inviting famous Confucian scholars to teach in Chang'an and allowing easy access to the capital for aspiring students. At the same time, he was also an avid believer in Buddhism and heavily promoted the religion in his state. In 401, he welcomed the Kuchean monk, Kumarajiva to his court, where he was highly honoured and became one of the most important translators of Sanskrit Buddhist texts into Chinese. It was also under the Later Qin in 399 when the monk Faxian departed from Chang'an for India to acquire Buddhist texts. Yao Xing built various temples and pagodas, with construction of the Maijishan Grottoes beginning under his reign, and records claim that around nine-tenths of the population in Later Qin practiced Buddhism.

Decline and fall
Upon reaching its peak, the Later Qin quickly declined due to pressure from its own vassals and the Eastern Jin. Yao Xing ceded twelves commaderies around the Han river at the request of Jin's paramount authority, Liu Yu, in exchange for peace, while giving up his holdings in the Hexi to the Southern Liang. In 407, he received Southern Yan and Western Shu's submissions, but lost Chouchi's allegicance to Jin. Worst of all, however, was the rebellion of the Xiongnu general, Helian Bobo, in the Ordos. Bobo established the Helian Xia, and for many years, led a war against Later Qin that drained their resources and killed many key generals. In 409, the Western Qin was revived in the Longxi, further reducing Later Qin's territory.

When Liu Yu led an expedition to conquer Southern Yan in 409, Yao Xing was powerless to stop him, leading to Southern Yan's demise in 410. He responded with an invasion of Jing province in conjunction with Western Shu and the Jin rebel, Lu Xun, but was defeated. Both Western Shu and Lu Xun were later vanquished by Jin, and Later Qin entered itself into a marriage alliance with the Northern Wei to protect itself.

Internally, Yao Xing also laid the seeds for a succession crisis. He appointed his eldest son, Yao Hong as Crown Prince, but only after much hesitation. He showed more favour to his other son, Yao Bi, who he gave military power and assigned to guard the borders while Yao Hong oversaw matters in Chang'an. Yao Bi attempted to take the throne on three occasions, all which ended in failure. He was forgiven after the first two attempts and was finally forced to commit suicide after the third in 416. However, Yao Hong still had other younger brothers and cousins who held military command and ambitions to seize power.

After Yao Xing died in 416, Yao Hong was immediately met with rebellions by his dukes. There were also revolts by the Xiongnu and Qiang tribes, and the Helian Xia, Chouchi and Western Qin all took the chance to attack Later Qin. To deal with the threats, Yao Hong entrusted military affairs to his great-uncle, Yao Shao who had much initial success, but the chaos soon caught the attention of Liu Yu. He began an expedition to conquer Later Qin, and by late 417, Yao Shao had died while Jin forces entered the Guanzhong and reached Chang'an. In the end, Yao Hong surrendered and was sent to the Jin capital, Jiankang, where he was executed. Members of the Yao clan who surrendered to Jin were exterminated, while the others who fled to Northern Wei survived.