Chiang Kai-shek in the context of "Second United Front"

The Second Sino-Japanese War was fought between the Republic of China and the Empire of Japan between 1937 and 1945, following a period of war localized to Manchuria that started in 1931. It is considered part of World War II, and often regarded as the beginning of World War II in Asia. It was the largest Asian war in the 20th century. It is known in China as the War of Resistance Against Japanese Aggression.

On 18 September 1931, the Japanese staged the Mukden incident, a false flag event fabricated to justify their invasion of Manchuria and establishment of the puppet state of Manchukuo. This is sometimes marked as the beginning of the war. From 1931 to 1937, China and Japan engaged in skirmishes, including in Shanghai and in Northern China. Nationalist and Chinese Communist Party (CCP) forces, respectively led by Chiang Kai-shek and Mao Zedong, had fought each other in the Chinese Civil War since 1927. In late 1933, Chiang Kai-shek encircled the Chinese Communists in an attempt to finally destroy them, forcing the Communists into the Long March, resulting in the Communists losing around 90% of their men. As a Japanese invasion became imminent, Chiang still refused to form a united front before he was placed under house arrest by his subordinates who forced him to form the Second United Front in late 1936 in order to resist the Japanese invasion together.

The Communist Party of China (CPC), commonly known as the Chinese Communist Party (CCP), is the founding and ruling party of the People's Republic of China (PRC). Founded in 1921, the CCP won the Chinese Civil War against the Kuomintang and proclaimed the establishment of the PRC under the chairmanship of Mao Zedong in October 1949. The CCP has since governed China and has had sole control over the country's armed forces and law enforcement. As of 2024, the CCP has more than 100 million members, making it the second largest political party by membership in the world.

In 1921, Chen Duxiu and Li Dazhao founded the CCP with the help of the Far Eastern Bureau of the Russian Communist Party (Bolsheviks) and Far Eastern Bureau of the Communist International. Although the CCP aligned with the Kuomintang (KMT) during its initial years, the rise of the KMT's right-wing under the leadership of Chiang Kai-shek and subsequent massacres of tens of thousands of CCP members resulted in a split and a prolonged civil war between the CCP and KMT. During the next ten years of guerrilla warfare, Mao Zedong rose to become the most influential figure in the CCP and the party established a strong base among the rural peasantry with its land reform policies. Support for the CCP continued to grow throughout the Second Sino-Japanese War. After the Japanese surrender in 1945, the CCP emerged triumphant in the communist revolution against the Nationalist government. The CCP established the People's Republic of China on 1 October 1949 and the remnants of the Nationalist government retreated to Taiwan shortly after.

The Kuomintang (KMT) is a major political party in the Republic of China (Taiwan). It was the sole ruling party of the country during its rule from 1927 to 1949 in Mainland China until its relocation to Taiwan, and in Taiwan ruled under martial law until 1987. The KMT is a centre-right to right-wing party and the largest in the Pan-Blue Coalition, one of the two main political groups in Taiwan. Its primary rival is the Democratic Progressive Party (DPP), the largest party in the Pan-Green Coalition. As of 2025, the KMT is the largest single party in the Legislative Yuan and is chaired by Cheng Li-wun.

The party was founded by Sun Yat-sen in 1894 in Honolulu, Hawaii, as the Revive China Society. He reformed the party in 1919 in the Shanghai French Concession under its current name. From 1926 to 1928, the KMT under Chiang Kai-shek successfully unified China in the Northern Expedition against regional warlords, leading to the fall of the Beiyang government. After initially allying with the Chinese Communist Party (CCP) in the First United Front, the party under Chiang purged communist members. It was the sole ruling party of China from 1928 to 1949 but gradually lost control while fighting the Empire of Japan in the Second Sino-Japanese War and the CCP in the Chinese Civil War. In December 1949, the Kuomintang retreated to Taiwan following its defeat by the communists.

The Northern Expedition was a military campaign launched by the National Revolutionary Army (NRA) of the Kuomintang (KMT) against the Beiyang government and other regional warlords in 1926. The purpose of the campaign was to reunify China, which had become fragmented in the aftermath of the 1911 Revolution. The expedition was led by Generalissimo Chiang Kai-shek, and was divided into two phases. The first phase ended in a 1927 political split between two factions of the KMT: the right-leaning Nanjing faction, led by Chiang, and the left-leaning faction in Wuhan, led by Wang Jingwei. The split was partially motivated by Chiang's Shanghai Massacre of Communists within the KMT, which marked the end of the First United Front. In an effort to mend this schism, Chiang Kai-shek stepped down as the commander of the NRA in August 1927, and went into exile in Japan.

The second phase of the Expedition began in January 1928, when Chiang resumed command. By April 1928, the nationalist forces had advanced to the Yellow River. With the assistance of allied warlords, including Yan Xishan and Feng Yuxiang, the nationalist forces secured a series of decisive victories against the Beiyang Army. As they approached Beijing, Zhang Zuolin, leader of the Manchuria-based Fengtian clique, was forced to flee and was later assassinated shortly thereafter by the Japanese. His son, Zhang Xueliang, took over as the leader of the Fengtian clique, and in December 1928, announced that Manchuria would accept the authority of the nationalist government in Nanjing. With the final piece of China under KMT control, the Northern Expedition concluded successfully and China was reunified, heralding the start of the Nanjing decade.

The "Four Policemen" was a postwar council with the Big Four that U.S. president Franklin D. Roosevelt proposed as a guarantor of world peace. Their members were called the Four Powers during World War II and were the four major Allies of World War II: the United Kingdom, the Soviet Union, the United States, and the Republic of China. Roosevelt repeatedly used the term "Four Policemen" starting in 1942.

The Four Policemen would be responsible for keeping order within their spheres of influence: Britain in its empire and Western Europe, the Soviet Union in Eastern Europe and the central Eurasian landmass, China in East Asia and the Western Pacific; and the United States in the Western Hemisphere. As a preventive measure against new wars, countries other than the Four Policemen were to be disarmed. Only the Four Policemen would be allowed to possess any weapons more powerful than a rifle.

Wang Zhaoming (4 May 1883 – 10 November 1944), widely known by his pen name Wang Jingwei, was a Chinese politician and poet who was president of the Reorganized National Government of the Republic of China, a puppet state of the Empire of Japan. He was initially a member of the left wing of the Kuomintang (KMT), leading a government in Wuhan in opposition to the centrist Nationalist government in Nanjing, but later became increasingly anti-communist after his efforts to collaborate with the Chinese Communist Party ended in political failure.

Wang was a close associate of Sun Yat-sen for the last twenty years of Sun's life. After Sun's death in 1925, Chiang Kai-shek, the leader of the centrist faction of Kuomintang, gradually became dominant among the party. Wang remained inside the Kuomintang, but continued to have disagreements with Chiang. Following the outbreak of the Second Sino-Japanese War in 1937, Wang accepted an invitation from the Japanese to form a collaborationist government in Nanjing, of which he served as the head of state until his death shortly before the End of World War II in Asia. Although he is still regarded as an important contributor in the 1911 Revolution, his collaboration with Imperial Japan is a subject of academic debate, and the typical narratives often regard him as a traitor with his name becoming synonymous with treason.

World War II officially ended in Asia on September 2, 1945, at 3:24 with the surrender of Japan on the USS Missouri. Before that, the United States dropped two atomic bombs on Japan, and the Soviet Union declared war on Japan, causing Emperor Hirohito to announce the acceptance of the Potsdam Declaration on August 15, 1945, which would eventually lead to the surrender ceremony on September 2.

After the ceremony, Japanese forces continued to surrender across the Pacific, with the last major surrender occurring on October 25, 1945, with the surrender of Japanese forces in Taiwan to Chiang Kai-shek. The American occupation of Japan lasted from the end of the war until April 28, 1952, when the Treaty of San Francisco came into effect.

The Nationalist government, Nationalist regime and Nationalist China, officially the National Government of the Republic of China, refer to the government of the Republic of China from 1 July 1925 to 20 May 1948, led by the nationalist Kuomintang (KMT) under Chiang Kai-shek.

Following the outbreak of the Xinhai Revolution, revolutionary leader Sun Yat-sen was elected to be China's provisional president and founded the Provisional Government of the Republic of China. To preserve national unity, Sun ceded the presidency to military strongman Yuan Shikai, who established the Beiyang government. After a failed attempt to install himself as Emperor of China, Yuan died in 1916, leaving a power vacuum which resulted in China being divided into several warlord fiefs and rival governments. They were nominally reunified in 1928 under the Nanjing-based government led by Chiang Kai-shek, which after the Northern Expedition initially governed the country as a one-party state under the Kuomintang, and was subsequently given international recognition as the legitimate representative of China, with Chiang as a de facto leader of the country under a military dictatorship. The Nationalist government would then experience many further challenges such as the Second Sino-Japanese War, and the Chinese Civil War. The government was in place until it was replaced by the current Government of the Republic of China in the newly promulgated Constitution of the Republic of China of 1947.