Chiang was an influential member of the Kuomintang (KMT), the Chinese Nationalist Party, as well as a close ally of Sun Yat-sen's. Chiang became the Commandant of the Kuomintang's Whampoa Military Academy and took Sun's place as leader of the KMT following the Canton Coup in early 1926. Having neutralized the party's left wing, Chiang then led Sun's long-postponed Northern Expedition, conquering or reaching accommodations with China's many warlords.
From 1928 to 1948, Chiang served as chairman of the National Military Council of the Nationalist Government of the Republic of China (ROC). Chiang was socially conservative, promoting traditional Chinese culture in the New Life Movement and rejecting both western democracy and Sun's nationalist democratic socialism in favour of an authoritarian government. Unable to maintain Sun's good relations with the communists, Chiang purged them in a massacre at Shanghai and repression of uprisings at Kwangtung and elsewhere.
At the onset of the Second Sino-Japanese War, which later became the Chinese theater of World War II, Zhang Xueliang kidnapped Chiang and obliged him to establish a Second United Front with the communists. After the defeat of the Japanese, the American-sponsored Marshall Mission, an attempt to negotiate a coalition government, failed in 1946. The Chinese Civil War resumed, with the Chinese Communist Party (CCP) led by Mao Zedong defeating the Nationalists and declaring the People's Republic of China in 1949. Chiang's government and army retreated to Taiwan, where Chiang imposed martial law and persecuted critics in a period known as the "White Terror". After evacuating to Taiwan, Chiang's government continued to declare its intention to retake mainland China. Chiang ruled Taiwan securely as President of the Republic of China and General of the Kuomintang until his death in 1975, just one year short of Mao's death.
Like Mao, Chiang is regarded as a controversial figure: supporters credit him with playing a major part in unifying the nation and a national figure of the Chinese resistance against Japan and the Allied victory of the Second World War, as well as his staunch anti-Soviet and anti-communist stance; detractors and critics denounce him as a dictator at the front of an authoritarian autocracy who suppressed and purged opponents and critics and arbitrarily incarcerated those he deemed as opposing to the Kuomintang among others.
Like many other Chinese historical figures, Chiang used several names throughout his life. That inscribed in the genealogical records of his family is Jiang Zhoutai (Chinese: 蔣周泰; Wade–Giles: Chiang Chou-t‘ai). This so-called "register name" (譜名) is the one under which his extended relatives knew him, and the one he used in formal occasions, such as when he got married. In deference to tradition, family members did not use the register name in conversation with people outside of the family. In fact, the concept of real or original name is not as clear-cut in China as it is in the Western world.
In honor of tradition, Chinese families waited a number of years before officially naming their offspring. In the meantime, they used a "milk name" (乳名), given to the infant shortly after his birth and known only to the close family, thus the actual name that Chiang received at birth was Jiang Ruiyuan (Chinese: 蔣瑞元; Wade–Giles: Chiang Jui-yuan).
In 1903, the 16-year-old Chiang went to Ningbo to be a student, and he chose a "school name" (學名). This was actually the formal name of a person, used by older people to address him, and the one he would use the most in the first decades of his life (as the person grew older, younger generations would have to use one of the courtesy names instead). Colloquially, the school name is called "big name" (大名), whereas the "milk name" is known as the "small name" (小名). The school name that Chiang chose for himself was Zhiqing (Chinese: 志清; Wade–Giles: Chi-ch‘ing, which means "purity of intentions"). For the next fifteen years or so, Chiang was known as Jiang Zhiqing (Wade-Giles: Chiang Chi-ch‘ing). This is the name under which Sun Yat-sen knew him when Chiang joined the republicans in Kwangtung in the 1910s.