The Shanghai massacre of 1927, also known as the April 12 Incident, was a large-scale purge of Communists from the Kuomintang (KMT) in Shanghai, ordered by Chiang Kai-shek on 12 April, 1927, during the Northern Expedition against the warlords.
In Chinese, the incident is called "the Purging of the Party" (清黨) by the Kuomintang (KMT), while the Communist Party of China (CPC) refers to it as the "Shanghai Massacre of 1927, "April 12 Anti-revolutionary Coup" (四一二反革命政变) or "April 12 Tragedy" (四一二慘案). Many prominent Communist members of the Kuomintang were imprisoned or executed by Chiang in an attempt to destroy the influence of the CCP. Over the several weeks following the April 12 incident in Shanghai, arrests and executions of prominent Communists spread across areas of China allied with Chiang, including a co-founder of the Chinese Communist Party, Li Dazhao, in Beijing. After defeating Communist insurrections in the cities, the Kuomintang became unified under Chiang's leadership, and went on to defeat the warlord factions and become dominant in China. The Communists withdrew to rural collectives, building strength in the countryside for the next phase of civil war.
For years prior to the purge, the Kuomintang (KMT) and the Communist Party of China (CPC) had cooperated within the First United Front to end the dominance of the warlords after the fall of the Qing Dynasty. In 1923, the government of Dr. Sun Yat-sen, founder of the Republic of China, accepted aid from the Soviet Union, after being denied recognition by the western powers. Soviet advisers, such as Mikhail Borodin, began to arrive in China in 1923 to aid in the reorganization of the KMT along the lines of the Communist Party of the Soviet Union. Members of the Communist Party of China were encouraged to join the Kuomintang, while maintaining their own CPC allegiance. With the assistance of the Comintern and Chinese Communist Party co-founders Li Dazhao and Chen Duxiu, Sun established the Kuomintang government in Guangzhou, and founded the Whampoa Military Academy to provide leadership for the National Revolutionary Army. Sun's favorite and rising star Chiang Kai-shek was appointed the first principal of the academy, and received military training in Moscow. Some CPC members became important leaders of Kuomintang; Zhou Enlai and Ye Jianying served as political instructors in the Whampoa Military Academy, and Mao Zedong as a KMT administrator in Hunan during this period.
After the death of Sun Yat-sen in 1925, a power struggle ensued between the right wing of the Kuomintang, led by Chiang Kai-shek, and the leftist and Communist faction of Wang Jingwei. Wang succeeded Sun as chairman of the national government, but Chiang became commander of the National Revolutionary Army. In July 1926, the Northern Expedition began, a Kuomintang military campaign to defeat the warlords controlling northern China and unify the country. Communists and leftist political administrators within the KMT began land reform favoring peasants in the areas conquered by the Northern Expedition army, thereby shifting support to the Chiang Kai-shek faction among wealthy landowners and foreign interests in Shanghai.
In January 1927, allied with the Chinese Communists and Soviet Agent Mikhail Borodin, Wang Jingwei and his KMT leftist allies captured the city of Wuhan and declared the seat of National Government there. On 3 March, 1927, workers led by Zhou Enlai launched an armed uprising in Shanghai, defeating the joint warlord forces of the Zhili clique and Shandong. The victorious workers occupied urban Shanghai except for the international settlements, prior to the arrival of the KMT army of Bai Chongxi, a close ally of Chiang. The right wing of the Kuomintang now became alarmed by the growth of Communist influence, both within the KMT government and the workers' militias of the cities. Taking advantage of international outrage over the Nanjing Incident in March, and with Shanghai under the control of Bai, Chiang momentarily halted his campaign against the warlords and decided to break with the leftists and Communists.
Chiang Kai-shek sent a military orchestra to entertain the workers' militia of the General Union of Shanghai Workers, while encouraging Du Yuesheng and other leaders of the Green Gang and the Hongmen Gang, to organize rightist groups to attack the unionists. On April 9, the Central Monitoring Committee declared an emergency condition in Shanghai, blaming the Communists of the Kuomintang government in Wuhan. A secret order was issued on April 11 to all provinces under the control of Chiang's forces to purge Communists from the KMT.
Before the sunrise of April 12, gang members attacked districts controlled by the workers, including Zhabei, Nanshi and Pudong. Under an emergency decree, the 26th Army disarmed the workers' militias, wounding more than 300 people. The unionists organized a mass meeting denouncing Chiang Kai-shek on April 13, and thousands of workers and students went to the headquarters of the 2nd Division of the 26th Army in protest. Soldiers opened fire, killing 100 and wounding many more. Chiang dissolved the government of Shanghai and the unions and other organizations under Communist control. Over a thousand Communists were arrested, some 300 were officially executed, and more than 5,000 went missing. Communists in Canton, Xiamen, Fuzhou, Ningbo, Nanjing, Hangzhou and Changsha were also arrested or killed. In Beijing on April 28, warlord Zhang Zuolin killed 20 Communists who had taken up refuge at the Soviet embassy, including Li Dazhao, co-founder of Chinese Communist Party.
After the April 12 Incident, Communist general-secretary Chen Duxiu and his Soviet advisors who had promoted cooperation with the KMT were discredited, but remained in power. The CPC prepared for an expected surge of worker revolution in the urban areas. The first battles of the 10-year Chinese Civil War began with armed Communist insurrections in Changsha, Shantou, Nanchang and Guangzhou. During the Nanchang Uprising in August 1927, Communist soldiers under Zhu De were defeated and escaped from Kuomintang forces by withdrawing to the mountains of western Jiangxi. In September 1927, Mao Zedong led a small peasant army in the Autumn Harvest Uprising in Hunan province. The uprising was defeated by Kuomintang forces and Mao's forces retreated to Jiangxi as well, forming the first elements of what would become the People's Liberation Army. By the time the CPC Central Committee was forced to flee Shanghai in 1933, Mao had established peasant-based soviets in Jiangxi and Hunan provinces, transforming the Communist Party's base of support from the urban proletariat to the countryside, where the people's war would be fought.