Sun Yat-sen was a Chinese physician, writer, philosopher, calligrapher and revolutionary, the first president and founding father of the Republic of China. As the foremost pioneer of the Republic of China, Sun is referred to as the "Father of the Nation" in the Republic of China (ROC), Hong Kong, Macau and the "forerunner of democratic revolution" in People's Republic of China (PRC). Sun played an instrumental role in the overthrow of the Qing dynasty during the years leading up to the Xinhai Revolution. He was appointed to serve as Provisional President of the Republic of China when it was founded in 1912. He later co-founded the Nationalist Party of China, serving as its first leader. Sun was a uniting figure in post-Imperial China, and he remains unique among 20th-century Chinese politicians for being widely revered amongst the people from both sides of the Taiwan Strait. Although Sun is considered to be one of the greatest leaders of modern China, his political life was one of constant struggle and frequent exile. After the success of the revolution, he quickly resigned from his post as President of the newly founded Republic of China due to Beiyang Clique pressure, and led successive revolutionary governments as a challenge to the warlords who controlled much of the nation. Sun did not live to see his party consolidate its power over the country during the Northern Expedition. His party, which formed a fragile alliance with the Communists, split into two factions after his death. Sun's chief legacy resides in his developing of the political philosophy known as the Three Principles of the People: nationalism (non-ethnic, independence from imperialist domination), modern government, and the people's livelihood (free trade and modern tax reform.