According to Sun Yat-sen's "Three Stages of Revolution" theory, the KMT was to rebuild China in three phases: the first stage was military unification, which was carried out with the Northern Expedition; the second was "political tutelage" which was a provisional government led by the KMT to educate people about their political and civil rights, and the third stage was the constitutional government. By 1928, the Nationalists, having taken over power militarily and reunified China, started the second phase, promulgating a provisional constitution and beginning the period of so-called "tutelage". The KMT was criticized for instituting authoritarianism, but claimed it was attempting to establish a modern democratic society.