Second Sino-Japanese War in the context of "Republic of China (1912–1949)"

World War II or the Second World War (1 September 1939 – 2 September 1945) was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were put on trial for war crimes.

The causes of World War II included unresolved tensions in the aftermath of World War I, the rise of fascism in Europe and militarism in Japan. Key events preceding the war included Japan's invasion of Manchuria in 1931, the Spanish Civil War, the outbreak of the Second Sino-Japanese War in 1937, and Germany's annexations of Austria and the Sudetenland. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland, after which the United Kingdom and France declared war on Germany. Poland was divided between Germany and the Soviet Union under the Molotov–Ribbentrop Pact. In 1940, the Soviet Union annexed the Baltic states and parts of Finland and Romania. After the fall of France in June 1940, the war continued mainly between Germany, now assisted by Fascist Italy, and the British Empire, with fighting in the Balkans, Mediterranean, and Middle East, the aerial Battle of Britain and the Blitz, and the naval Battle of the Atlantic. Through campaigns and treaties, Germany gained control of much of continental Europe and formed the Axis alliance with Italy, Japan, and other countries. In June 1941, Germany invaded the Soviet Union, opening the Eastern Front and initially making large territorial gains.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, Soviet Union, United States, and China.

Membership in the Allies varied during the course of the war. When the conflict broke out on 1 September 1939, the Allied coalition consisted of the United Kingdom, France, and Poland, as well as their respective dependencies, such as British India. They were joined by the independent dominions of the British Commonwealth: Canada, Australia, New Zealand and South Africa. Consequently, the initial alliance resembled that of the First World War. As Axis forces began invading northern Europe and the Balkans, the Allies added the Netherlands, Belgium, Norway, Greece, and Yugoslavia. The Soviet Union, which initially had a nonaggression pact with Germany and participated in its invasion of Poland, joined the Allies after the German invasion of the Soviet Union in June 1941. The United States, while providing some material support to European Allies since September 1940, remained formally neutral until the Japanese attack on Pearl Harbor in December 1941, after which it declared war and officially joined the Allies. China had already been at war with Japan since 1937, and formally joined the Allies in December 1941.

The causes of World War II have been given considerable attention by historians. The immediate precipitating event was the invasion of Poland by Nazi Germany on September 1, 1939, and the subsequent declarations of war on Germany made by Britain and France, but many other prior events have been suggested as ultimate causes. Primary themes in historical analysis of the war's origins include the political takeover of Germany in 1933 by Adolf Hitler and the Nazi Party; Japanese militarism against China, which led to the Japanese invasion of Manchuria and the Second Sino-Japanese War; Italian aggression against Ethiopia, which led to the Second Italo-Ethiopian War; or military uprising in Spain, which led to the Spanish Civil War.

During the interwar period, deep anger arose in the Weimar Republic over the conditions of the 1919 Treaty of Versailles, which punished Germany for its role in World War I with heavy financial reparations and severe limitations on its military that were intended to prevent it from becoming a military power again. The demilitarisation of the Rhineland, the prohibition of German unification with Austria, and the loss of its overseas colonies as well as some 12% of the pre-war land area and population of the metropole all provoked strong currents of revanchism in German politics.

Yasukuni Shrine (Japanese: 靖国神社 or 靖國神社, Hepburn: Yasukuni Jinja; lit. 'Peaceful Country Shrine') is a Shinto shrine located in Chiyoda, Tokyo. It was founded by Emperor Meiji in June 1869 and commemorates those who died in service of Japan, from the Boshin War of 1868–1869, to the two Sino-Japanese Wars, 1894–1895 and 1937–1945 respectively, and the First Indochina War of 1946–1954. The shrine's purpose has been expanded over the years to include those who died in the wars involving Japan spanning from the entire Meiji and Taishō periods, and the earlier part of the Shōwa period.

The shrine lists the names, origins, birthdates and places of death of 2,466,532 people. Among those are 1,066 convicted war criminals from the Pacific War, twelve of whom were charged with Class A crimes (the planning, preparation, initiation, or waging of the war). Eleven were convicted on those charges, with the twelfth found not guilty on all such charges, though he was found guilty of Class B war crimes. The names of two more men charged with Class A war crimes are on the list, but both died before they could be sentenced (one died during trial and one before trial), so they were never convicted.

The history of the island of Taiwan dates back tens of thousands of years to the earliest known evidence of human habitation. The sudden appearance of a culture based on agriculture around 3000 BC is believed to reflect the arrival of the ancestors of today's Taiwanese indigenous peoples. People from China gradually came into contact with Taiwan by the time of the Yuan dynasty (1271–1368) and Han Chinese people started settling there by the early 17th century. The island became known by the West when Portuguese explorers discovered it in the 16th century and named it Formosa. Between 1624 and 1662, the south of the island was colonized by the Dutch headquartered in Zeelandia in present-day Anping, Tainan whilst the Spanish built an outpost in the north, which lasted until 1642 when the Spanish fortress in Keelung was seized by the Dutch. These European settlements were followed by an influx of Hoklo and Hakka immigrants from Fujian and Guangdong.

In 1662, Koxinga defeated the Dutch and established a base of operations on the island. His descendants were defeated by the Qing dynasty in 1683 and their territory in Taiwan was annexed by the Qing dynasty. Over two centuries of Qing rule, Taiwan's population increased by over two million and became majority Han Chinese due to illegal cross-strait migrations from mainland China and encroachment on Taiwanese indigenous territory. Due to the continued expansion of Chinese settlements, Qing-governed territory eventually encompassed the entire western plains and the northeast. This process accelerated in the later stages of Qing rule when settler colonization of Taiwan was actively encouraged. The Qing ceded Taiwan and Penghu to Japan after losing the First Sino-Japanese War in 1895. Taiwan experienced industrial growth and became a productive rice- and sugar-exporting Japanese colony. During the Second Sino-Japanese War it served as a base for invasions of China, and later Southeast Asia and the Pacific during World War II.

East China (Chinese: 华东; pinyin: huá dōng) is a geographical region in the People's Republic of China, mainly consisting of seven province-level administrative divisions, namely the provinces (from north to south) Shandong, Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, and the direct-administered municipality Shanghai.

The region was defined in 1945 as the jurisdiction area of the Central Committee's East China Bureau (华东局), which was a merger politburo agency of the Shandong Bureau and the Central China Bureau previously established during the Second Sino-Japanese War. After the founding of the People's Republic of China, the region included all the aforementioned provinces except Jiangxi, which was previously considered part of South Central China before being reassigned in 1961. The East China Bureau was abolished in 1966 due to the Cultural Revolution, but in 1970 the fourth five-year plan redefined the region as the East China Coordinated Region (华东协作区), which supported the logistics of the Jinan and Nanjing Military Regions. This geographical definition was retained after the economic reform of the 1980s.

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 Chinese Civil War was fought between the Kuomintang-led government of the Republic of China and the forces of the Chinese Communist Party (CCP). Armed conflict continued intermittently from 1 August 1927 until Communist victory resulted in their total control over mainland China on 10 December 1949.

The war is generally divided into two phases with an interlude: from August 1927 to 1937, the First United Front alliance of the KMT and CCP collapsed during the Northern Expedition, and the Nationalists controlled most of China. From 1937 to 1945, hostilities were mostly put on hold as the Second United Front fought the Japanese invasion of China with eventual help from the Allies of World War II. However, armed clashes between the groups remained common. Exacerbating the divisions within China further was the formation of the Wang Jingwei regime, a Japan-sponsored puppet government led by Wang Jingwei, which was established to nominally govern the regions of China that came under Japanese occupation.

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.