The Southern and Northern Dynasties

Preceded by the Eastern Jin Dynasty (317-420) and followed by the Sui Dynasty (58-618), the Southern and Northern Dynasties lasted from 420 to 589, which was a time of turmoil and war, but it was also a time of prosperity for art, culture, religion and technology in the history of China.
The Southern Dynasties (420-589) refer to the Liu Song Dynasty (420-479), the Southern Qi Dynasty (479-502), the Liang Dynasty (502-557) and the Chen Dynasty (557-589); the Northern Dynasties (386-581) include the North Wei (386-557), the East Wei (534-550), the West Wei (535-556), the North Qi (550-577) and the North Zhou (557-581) dynasties.
Although there were unceasing social disorders, frequent changes of dynasties and unexpected natural disasters, the Southern Dynasties (420-589) and the Northern Dynasties (386-581) remained in stalemate for over 100 years, and the historians called this period the Southern and Northern Dynasties (420-589).
The Southern Dynasties (420-589)
China was divided into South China and North China in 304, which confronted each other. Four dynasties stepped onto the historical stage successively in North China — the Liu Song Dynasty (420-479), the Southern Qi Dynasty (479-502), the Liang Dynasty (502-557) and the Chen Dynasty (557-589) — which were known as the Southern Dynasties (420-589) in Chinese history.
All of the four dynasties had their capitals in Jiangkang (presently Nanjing of Jiangsu Province), except that Emperor Yuan of the Liang Dynasty (502-557) had his capital at Jiangliang (presently Jiangling of Hubei Province) for three years.
The Longmen Grottoes.
The Southern Dynasties (420-589) was a changing period for the nobilities from prosperity to decline. Though the nobilities still enjoyed a very high social status in the Southern Dynasties (420-589), they couldn't completely control the political situation owing to the increasingly strengthened imperial power.
With the areas to the south of the Yangtze River becoming further developed, more and more Han people from the lower class stepped into the bureaucratic ranks and received the pleasure of the emperors during the Southern Dynasties (420-589).
Liu Song
As the longest dynasty among the Southern Dynasties (420-589), the Liu Song Dynasty (420-479) was founded by Liu Yu, a general of the Northern Garrison Army of the Eastern Jin Dynasty (317-420), who came into power through suppressing Huan Xuan's rebellion in 404. He didn't even hesitate to lead two northern expeditions against North China just to gain prestige, during which he seized the territories of Henan, Shandong and Guanzhong (the lower valley of the Wei River).
By killing Emperor An (Sima Dezong) and deposing Emperor Gong (Sima Dewen) of the Eastern Jin Dynasty (317-420), Liu Yu crowned himself Emperor Wu of the Liu Song Dynasty (420-479) on July 10th of 420, thus ending the Eastern Jin Dynasty (317-420) and establishing the Southern Dynasties (420-589). Tuoba Gui of the North Wei Dynasty (386-557) unified North China in 440, since the confrontation between North China and South China had begun.
Emperor Wu was very frugal after ascending the throne, but he was not interested in royal education and trusted unworthy men, leading to a great disaster in his court. After realizing the imperial power was threatened by the nobilities, Emperor Wu started to promote humble clan landlords to higher official positions and gave military power to his kinsmen. Owing to his kinsmen often plotting to overthrow him, Emperor Wu was so terrified that he frequently had them killed.
Emperor Wu abdicated the throne in favor of his son, Liu Song (later Emperor Shao), who was deposed and later killed by his men, Xu Xianzhi and Fu Liang, owing to his immoral behavior. The courtiers set up Liu Yilong (another son of Emperor Wu) as Emperor Wen of the Liu Song Dynasty (420-479).
Emperor Wen later had Xu Xianzhi and Fu Liang killed with the help of General Tan Daoji (a general of the Northern Garrison Army), and during his reign the political situation was rather stable owing to his cleansing of political corruption and advocating frugality; this period was known as the Yuanjia Administration in the history of China.
Emperor Wen had launched several northern expeditions against the North Wei Dynasty (386-557) since 430, ending up with failure each time owing to insufficient preparations and inadequate commands, which had greatly weakened his kingdom. On the contrary, the North Wei Dynasty (386-557) crusaded against the Liu Song Dynasty (420-479) and conquered the Yangtze River area in 445, following which the Liu Song Dynasty (420-479) remained in a weakened state.
Emperor Wen was murdered by the crown prince, Liu Shao, in 453. The third son of Emperor Wen, Liu Jun, killed Liu Shao, crowning himself as Emperor Xiaowu of the Liu Song Dynasty (420-479), but he was very licentious and cruel and even raped his own niece, leading to his kinsmen's rebellion, and he slaughtered them all in Guangling (presently Yangzhou of Jiangsu Province).
After the death of Emperor Xiaowu, Liu Ziye (later Emperor Qianfei of the Liu Song Dynasty) ascended the throne, ordering his own kinsmen to be killed which eventually resulted in his assassination by Liu Yu. After usurping the throne, Liu Yu crowned himself as Emperor Ming of the Liu Song Dynasty (420-479) and killed all the descendants of Emperor Xiaowu.
As the son of Emperor Ming, Liu Yu (later Emperor Houfei of the Liu Song Dynasty) ascended the throne and the military power fell into the hands of Xiao Daocheng. By deposing Emperor Houfei and setting up Liu Huai (the third son of Emperor Ming) as a puppet emperor, Xiao Daocheng arrogated all powers to himself.
After crushing his political opponents, Yuan Can and Shen Youzhi, Xiao Daocheng deposed Liu Huai and crowned himself Emperor Gao of the Southern Qi Dynasty (479-502), symbolizing the demise of the Liu Song Dynasty (420-479).
Southern Qi
The Southern Qi Dynasty (479-502) was established by