Founder of the Song-dynasty was General Zhao Kuangyin. He was proclaimed emperor by his troops in Kaifeng in 960. Kaifeng became capital of the Song-empire, which was able to unite whole of China during the following 20 years. The first emperor got the emperor name Taizu. However, regarding foreign affairs, the Song dynasty was not able to continue the successes the Tang dynasty had.
The expansion was stopped in the north by the empire of the Kitan, while in northwest, Tibet succeeded in defending itself against the Song-troops. Vietnam very early came beyond Chinas control, and Korea and Mongolia too could not be conquered by the Song-empire. The Dali-empire in the province Yunnan could successfully defend itself, until centuries later; it was finally taken by the Mongols.
The first Song-emperor died in 976, his successor initially continued with his politics of conquest, and did consolidate the empire after the successful reunification. The Kitan in the north were rather strengthened by the relatively peaceful politics of the Song, thus finally becoming more and more a problem for the third emperor of the Song-dynasty, Zhengzhong.
They undertook series of robberies in the Chinese provinces Hebei and Shanxi and could only be kept in check by giving them tribute payments. The Mongols too became dangerously threatening as of the mid 11th century. They united to form an empire (western Xia-dynasty), which included southern Mongolia as well as the provinces Shanxi, Shenxi and Gansu.
The final decline of the Song-dynasty started very early, namely at that point where military threads from outside were added, and due to the expensive peace negotiations an economical crisis kicked off. The campaign against Kitan, which was planned long beforehand, had to be deferred due to rebellions and could finally be won only with help of the Jurchens. These indeed knew to use this through ball, namely the obvious weak state of the Chinese troops, and captured the capital Kaifeng.
The followers of the Song-dynasty flew the country towards the south and made the town Nanjing the capital of the Southern Song-dynasty (1127-1279). However, little time later, Hangzhou (province Zhjiang) became capital. Meanwhile the Jurchens founded the Jin-dynasty in the north of the country; capital of this dynasty was Beijing.
The time of the southern Song-dynasty
In the south, the Song dynasty could hold their empire for further 150 years. The new emperor of the Song had the task to consolidate the empire and to strike back any attacks undertaken by the Jurchens, who advanced as far as to the Yangtze River. Yue Fei, a Chinese general played an important role in fending off the various arracks and he even succeeded in undertaking campaigns that led deeply into the hostile hinterland.
However, at the end of the day, all efforts in winning back the north were finally abandoned. It was the chancellor Qin Gui, who finally convinced the emperor to embark on politics that would rather opt for consolidation and appeasement.
In 1276, the reign of the southern Song was finally brought to an end with the Mongols capturing Hangzhou.