Republic of China (ROC), was a country in East Asia based in Mainland China from 1912 to 1949, prior to the relocation of its government to Taiwan as a result of the Chinese Civil War. At a population of 541 million in 1949, it was the world's most populous country. Covering 11.4 million square kilometres (4.4 million square miles),it consisted of 35 provinces, 1 special administrative region, 2 regions, 12 special municipalities, 14 leagues, and 4 special banners. This period is often referred to as the Republican Era in Mainland China or the Mainland Period in Taiwan.(FROM WIKIPEDIA) This is the official flag of ROC in 1912-1928,as known the 5-colored Flag.