The Shanghai massacre of April 12, 1927, known commonly in China as the April 12 Purge or April 12 Incident, was the violent suppression of Communist Party of China (CPC) organizations in Shanghai by the military forces of Generalissimo Chiang Kai-shek and conservative factions in the Kuomintang (Nationalist Party, or KMT). Following the incident, conservative KMT elements carried out a full-scale purge of Communists in all areas under their control, and even more violent suppression occurred in Guangzhou and Changsha. The purge led to an open split between left and right wing factions in the KMT, with Chiang Kai-shek establishing himself as the leader of the right wing faction based in Nanjing, in opposition to the original left-wing KMT government based in Wuhan led by Wang Jingwei.
By 15 July 1927, the Wuhan regime had also expelled the Communists in its ranks, effectively ending the KMT's four-year alliance with the Comintern and the Chinese Communist Party. For the remainder of 1927, the CPC launched several uprisings in an attempt to regain their previous power, marking the beginning of the Chinese Civil War. With the failure of the Guangzhou Uprising however, the Communist Party was largely diminished in their influence, unable to launch another major urban offensive.
In KMT historiography, the event is occasionally referred to as "April 12 Purge" (四一二清黨), while the Communist historiography refers to the event in the form of "April 12 Counter-revolutionary Coup" (四一二反革命政變) or "April 12 Massacre" (四一二慘案).
The roots of the April 12 Incident go back to the Kuomintang's alliance with the Soviet Union, formally initiated by KMT founder Sun Yat-sen after discussions with Soviet diplomat Adolph Joffe in January 1923. This alliance included both financial and military aid and a small but important group of Soviet political and military advisors, headed by Mikhail Borodin. The Soviet Union's conditions for alliance and aid included cooperation with the small Communist Party of China. Sun agreed to let the Communists join the KMT as individuals, but ruled out an alliance with them or their participation as an organized bloc; in addition, once in the KMT he demanded that the Communists support KMT's party ideology and observe party discipline. Following their admission, Communist activities within the KMT, often covert, soon attracted opposition to this policy among prominent KMT members. Internal conflicts between left- and right-wing leaders of the KMT with regards to the CPC problem continued right up to the launch of the Northern Expedition.
Plans for a Northern Expedition originated with Sun Yat-sen. After his expulsion from the government in Peking, by 1920 he had made a military comeback, gaining control of some parts of Guangdong province. His goal was to extend his control over all of China, particularly Peking. After Sun's death from cancer in March 1925, KMT leaders continued to push the plan, and—after purging Guangzhou's Communists and Soviet advisors during the "Canton Coup" on 20 May 1926—finally launched the Expedition that June. Initial successes in the first months of the Expedition soon saw the KMT's National Revolutionary Army (NRA) in control of Guangdong and large areas in Hunan, Hubei, Jiangxi and Fujian.
With the growth of KMT authority and military strength, the struggle for control of the Party's direction and leadership intensified. In January 1927 the NRA commanded by Chiang Kai-shek captured Wuhan and went on to attack Nanchang, while KMT leader Wang Jingwei and his left-wing allies, along with the Chinese Communists and Soviet agent Borodin, transferred the seat of the Nationalist Government from Guangzhou to Wuhan. On March 1 the Nationalist government reorganized the Military Commission and placed Chiang under its jurisdiction, while secretly plotting to arrest him. Chiang found out about this plot, which most likely led to his determination to purge the CPC from KMT.
In response to the advances of the NRA, Communists in Shanghai began to plan uprisings against the warlord forces controlling the city. On March 21–22 KMT and CPC union workers led by Zhou Enlai and Chen Duxiu launched an armed uprising in Shanghai, defeating the warlord forces of the Zhili clique. The victorious union workers occupied and governed urban Shanghai except for the international settlements prior to the arrival of the NRA's Eastern Route Army led by Gen. Bai Chongxi and Gen. Li Zongren. After the Nanking Incident, in which foreign concessions in Nanjing were attacked and looted, both the right wing of the Kuomintang and western powers became alarmed by the growth of Communist influence, while the CP continued to organize daily mass student protests and labor strikes, demanding the return of Shanghai international settlements to Chinese control. With Bai's army firmly in control of Shanghai, on April 2 the Central Control Commission of KMT, led by former Chancellor of Peking University Cai Yuanpei, determined that the CPC actions were anti-revolutionary and undermined the national interest of China, and voted unanimously to purge the Communists from the KMT.
On April 5 Wang Jingwei arrived in Shanghai from overseas and met with the CPC leader Chen Duxiu. After their meeting they issued a joint declaration re-affirming the principle of cooperation between the KMT and the CPC, despite urgent pleas from Chiang and other KMT elders to eliminate Communist influence. When Wang left Shanghai for Wuhan the next day, Chiang asked Green Gang leader Du Yuesheng and other gang leaders in Shanghai to form a rival union to oppose the Shanghai labor union controlled by the Communists, and made final preparations for purging CPC members.
On April 9 Chiang declared martial law in Shanghai and the Central Control Commission issued the "Party Protection and National Salvation" proclamation, denouncing the Wuhan Nationalist Government's policy of cooperation with the CPC. On April 11 Chiang issued a secret order to all provinces under the control of his forces to purge Communists from the KMT.
Before dawn on April 12, gang members began to attack district offices controlled by the union workers, including Zhabei, Nanshi and Pudong. Under an emergency decree, Chiang ordered the 26th Army to disarm the workers' militias; that resulted in more than 300 people being killed and wounded. The union workers 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 to protest. Soldiers opened fire, killing 100 and wounding many more. Chiang dissolved the provisional government of Shanghai, labor unions and all other organizations under Communist control, and reorganized a network of unions with allegiance to the Kuomintang and under the control of Du Yuesheng. Some sources say that over 1000 Communists were arrested, some 300 were executed and more than 5,000 went missing; others claim 5,000-10,000 killed. Western news reports later nicknamed Gen. Bai "The Hewer of Communist Heads". Some National Revolutionary Army commanders with Communist backgrounds who were graduates of Whampoa Military Academy kept their sympathies for the Communists hidden and were not arrested, and many switched their allegiance to the CPC after the start of the Chinese Civil War.
For the Kuomintang, 39 members of the Kuomintang Central Committee in Wuhan publicly denounced Chiang Kai-shek as a traitor to Sun Yat-sen, including Sun's widow Soong Ching-ling immediately after the purge. However, Chiang was defiant, forming a new Nationalist Government at Nanjing to rival the Communist-tolerant Nationalist Government in Wuhan controlled by Wang Jingwei on April 18. The purges garnered the Nanjing government the support of much of the NRA, the Chinese merchant class, and foreign businesses, bolstering its economic and military position.
The twin rival KMT governments, known as the Ninghan (Nanjing and Wuhan) Split (Chinese: 宁汉分裂), did not last long. In May 1927 Communists and peasant leaders in the Wuhan area were repeatedly attacked by Nationalist generals. On June 1, Stalin sent a telegram to the Communists in Wuhan, calling for mobilisation of an army of workers and peasants. This alarmed Wang Jingwei, who decided to break with the Communists and come to terms with Chiang Kai-shek.
More than 10,000 communists in Canton, Xiamen, Fuzhou, Ningbo, Nanjing, Hangzhou and Changsha were arrested and executed within 20 days. The Soviet Union officially terminated its cooperation with the KMT while Wang, fearing retribution as a Communist sympathizer, fled to Europe. The Wuhan Nationalist government soon disintegrated, leaving Chiang as the sole legitimate leader of the Kuomintang. In the years after April 1927, 300,000 people were killed across China in three years of warfare against the Communists as many She people and Hakka people had their whole families killed including infants and women sold to prostitution.
On the Communists' side, Chen Duxiu and his Soviet advisers, who had promoted cooperation with the KMT, were discredited and lost their leadership roles in the CPC. Chen was personally blamed, forced to resign and replaced by Qu Qiubai, who did not change Chen's policies in any fundamental way. The CPC planned for worker uprisings and revolutions in the urban areas.
The first battles of the ten-year Chinese Civil War began with armed Communist insurrections in Changsha, Shantou, Nanchang and Guangzhou. During the Nanchang Uprising in August Communist troops under Zhu De were defeated but escaped from Kuomintang forces by withdrawing to the mountains of western Jiangxi. In September Mao Zedong led a small peasant army in what has come to be called the Autumn Harvest Uprising in Hunan province. It was defeated by Kuomintang forces and the survivors 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.
In June 1928 the National Revolutionary Army captured the Beiyang Government's capital of Beijing, leading to the nominal unification of China and worldwide recognition of the Kuomintang led by Chiang Kai-shek as the legal government of the Republic.