During the 100 years following the Opium War, the imperialist powers launched wars of aggression against China many times. At the same time, resistance movements emerged, such as that of the Taiping Heavenly Kingdom, the Reform Movement of 1898 and the Yihetuan Movement. Among all these movements that which had the greatest significance was the Revolution of 1911 led by Dr. Sun Yat-sen, which overthrew the 2,000-year-old autocratic feudal monarchy, and established the Republic of China. The May 4 Movement of 1919 laid the groundwork for the foundation of the Chinese Communist Party, which finally liberated China from imperialist oppression in 1949.