Shifting Claims on "China"

Important Dates:  
221 BCE New centralized state in northern plains region under the Qin ruler who took the new title of huangdi, emperor.
3rd cent. BCE Qin emperor orders construction of Great Wall to protect new empire from nomad warriors
206 BCE-220 AD Han dynasty founded; military campaigns conquer vast territories, incl. what is now N. Vietnam, Korea, Inner Mongolia, Xinjiang; Consolidate notion of "The Middle Kingdom" surrounded by barbarians.
3rd-6th cent. AD "Period of disunion".  Region splinters into a variety of contending polities.
581-617 AD Sui Dynasty. Plains region reunified by shortlived dynasty.
618-907 AD Tang dynasty, new capitals at Chang 'an and Loyang; reunites vast territories previously carved up into competing regimes; claims Tibet as vassal state.
907-960 AD Five Dynasties.  Region splinters into a variety of contending polities.
960-1279 AD Song dynasty; elite Chinese culture and administrative system flourishes, but territories lost to non-Chinese states.
1279-1368 AD Yuan dynasty; Mongols under Ghenghis Khan conquer whole territory, rule vast empire with Chinese-style administrative system and officials.
1368-1644 AD Ming dynasty; Chinese rebels retake China, capital in Nanjing; formalized tribute system with over 40 other "vassal" states.
1644-1911 AD Qing dynasty; Manchus from north conquer China, administer empire with Chinese-style system, adopt Chinese elite culture.  Great prosperity and expansion of some administrative control into Tibetan regions.
1911-1949 AD Republican Era; Tumultuous period of nation-building; political control collapses into competing warlords and civil war between KMT (Guomindang, "Republican Party") and CCP.  Threats and humiliating defeats from imperialist Japan and western states.
1912 Founding of the Republic of China. Revolutionary activist Sun Yat-sen, in exile in the U.S., returned to be elected the first president. But Yuan Shikai, head of the northern military, proclaimed himself emperor later that year and Sun, after leading an unsuccessful revolt, fled to Japan, where he organized the Republican Party (Guomindang, KMT). Centralized control collapses. Competing warlords control most of the north.
May 4, 1919 May Fourth Movement; Chinese students and merchants protest post-WWI Treaty of Versailles and Japanese interference, new national identities emerge.
1937 Japanese invasion and occupation of Manchuria (NE China).
1949 CCP wins civil war with the KMT; establishes the "multinational state" of the People's Republic of China (Zhonghua Renmin Gonghe Guo).
1950-1 Communist troops attack borders of central Tibet, Tibetans surrender and sign "17-Point Agreement" acknowledging Chinese sovereignty and claiming Tibet will be protected from communist reforms.
1953 Chinese scholars begin massive effort to investigate and define "minzu" groups in the PRC.  400 different groups initially claim separate identities; 56 eventually recognized by the state, with "Han" defined as the majority, all others as "minority" minzu.  Tibetans called "Zangzu".