Chinese irredentism refers to irredentist claims to territories of the former Chinese Empire made by the Republic of China (ROC) and subsequently the People's Republic of China (PRC). History In Chinese political theory, relations between foreign states were governed by the tributary system. Since the Emperor of China held the Mandate of Heaven, his rule was universal and extended to all under Heaven. Sometimes neighboring states were actual protectorates or vassal states over which Chinese dynasties exerted large amount of influence, while in other cases foreign states merely acknowledged China's nominal suzerainty in order to gain access to Chinese trade, which took place through the tributary system. Qin dynasty Ying Zheng of the state of Qin first unified the Chinese states to form the Chinese Empire in 221 BC. Under the Qin dynasty, China expanded southward and northward, clashing with ancient Baiyue, Dongyi and Xiongnu peoples. Han dynasty The Han dynasty expanded southward and established control over Vietnam. It also ruled over northern Korea and the Tarim Basin. Sui dynasty The Sui dynasty attempted to expand into the Korean Peninsula but was stopped after disastrous campaigns that contributed to the collapse of the dynasty. The Sui dynasty also reincorporated Vietnam and attacked Champa. Tang dynasty The Tang dynasty expanded greatly into Central Asia as far west as the Caspian Sea. The Tang dynasty aided Silla in defeating Goguryeo and Baekje, and the Tang subsequently established the Protectorate General to Pacify the East, the Ungjin Commandery, and the Gyerim Territory Area Command on the Korean Peninsula. In the north, the Tang dynasty extended its control into the Mongolian Plateau and southern Siberia with the Protectorate General to Pacify the North. Song dynasty The Song dynasty, in securing maritime trade routes that ran from Southeast Asia into the Indian Ocean, had established fortified trade bases in the Philippines. It also sought to reclaim Vietnam and various northern heartland from the rivalling Jin dynasty, but the campaigns were unsuccessful. Yuan dynasty The Yuan dynasty incorporated northern Burma and Tibet into China. It also established the Zhengdong Province on the Korean Peninsula and ruled the area through the vassal kings of the Goryeo dynasty. However, its failed invasion of Vietnam and Japan, among others, led to the end of Yuan expansionist desires. Ming dynasty During the Ming dynasty, Chinese rule over Vietnam was re-established, but it lasted only 20 years and ended when Ming