Northern Expedition

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.

In the 1920s, the Beiyang government based in Beijing was internationally recognised as the legitimate Chinese government. Much of the country, however, was not under its control, being ruled by a patchwork of warlords. The Kuomintang (KMT), based in Guangzhou (Canton), aspired to be the party of national liberation. Since the conclusion of the Constitutional Protection Movement in 1922, the KMT had been bolstering its ranks to prepare for an expedition against the northern warlords in Beijing, with the goal of reunifying China. This preparation involved improving both the political and military strength of the KMT. Before his death in March 1925, Sun Yat-sen, the founder of the Republic of China and co-founder of the KMT, was supportive of Sino-Soviet co-operation, which had involved forming the First United Front with the Chinese Communist Party (CCP). The military arm of the KMT was the National Revolutionary Army (NRA). Chiang Kai-shek, who had emerged as Sun's protégé as early as 1922, was appointed commandant of the Whampoa Military Academy in 1924, and quickly emerged as a contender for the position of Sun's successor in the aftermath of his death.

On 30 May 1925, Chinese students in Shanghai gathered at the International Settlement, and held demonstrations in opposition to foreign interference in China. Specifically, with the support of the KMT, they called for the boycott of foreign goods and an end to the Settlement, which was governed by the British and Americans. The Shanghai Municipal Police, largely operated by the British, opened fire on the crowd of demonstrators. This incident sparked outrage throughout China, culminating in the Canton–Hong Kong strike, which began on 18 June 1925, and proved a fertile recruiting ground for the CCP. Concerns about the rising power of the leftist faction and the effect of the strike on the Guangzhou government's ability to raise funds, which was largely dependent on foreign trade, led to increasing tensions within the United Front. Amidst this backdrop, Chiang, who had been vying for the position of KMT leader, began to consolidate power in preparation for an expedition against the northern warlords. On 20 March 1926, he launched a bloodless purge of hardline communists who were opposed to the proposed expedition from the Guangzhou administration and its military, known as the Canton Coup. At the same time, Chiang made conciliatory moves toward the Soviet Union, and attempted to balance the need for Soviet and CCP assistance in the fight against the warlords with his concerns about growing communist influence within the KMT. In the aftermath of the coup, Chiang negotiated a compromise whereby hardline members of the rightist faction, such as Wu Tiecheng, were removed from their posts in compensation for the purged leftists. By doing so, Chiang was able to prove his usefulness to the CCP and their Soviet sponsor, Joseph Stalin. Soviet aid to the KMT government would continue, as would co-operation with the CCP. A fragile coalition between KMT rightists, centrists led by Chiang, KMT leftists, and the CCP managed to hold together, laying the groundwork for the Northern Expedition.

In 1926, there were three major coalitions of warlords across China that were hostile to the KMT government in Guangzhou. The forces of Wu Peifu occupied the northern Hunan, Hubei, and Henan provinces. The coalition of Sun Chuanfang was in control of the Fujian, Zhejiang, Jiangsu, Anhui, and Jiangxi provinces. The most powerful coalition, led by Zhang Zuolin, then head of the Beiyang government and the Fengtian clique, was in control of Manchuria, Shandong, and Zhili. To face the Northern Expedition, Zhang Zuolin eventually assembled the "National Pacification Army" (Chinese: 安國軍; pinyin: Ānguójūn; Wade–Giles: Ankuochün; NPA), an alliance of the warlords of northern China.

Amidst heavy fighting along the border between KMT-held territory and that of the recently allied forces of the Fengtian and Zhili cliques, the nationalist government appointed Chiang Kai-shek commander-in-chief of the NRA on 5 June 1926. Chiang would accept this post in a ceremony on 9 July, which marked the formal start of the Northern Expedition, although military clashes had already been ongoing. The initial strategy for the KMT's northern advance against the Zhili warlords, which was largely devised by Soviet advisors Mikhail Borodin and Vasily Blyukher, was to focus on defeating Wu Peifu and appeasing Sun Chuanfang, while ignoring Zhang Zuolin of the Fengtian clique. Having switched from a defensive to offensive posture, KMT forces quickly advanced from their base in Guangdong into Wu-controlled Hunan province, capturing Changsha on 11 July. At the time, most of Wu Peifu's forces were preoccupied with fighting at Nankou Pass, near Beijing, against the Guominjun, a breakaway Zhili faction sympathetic to the KMT. Sun Chuanfang, who the KMT had avoided antagonising, did not intervene as KMT troops advanced further into Wu's territory. Whilst the Fengtian clique had offered its support to Wu, he refused their aid, fearing that the northern warlords would undermine his position if he allowed their troops into his territory. At a military conference held in Changsha on 11–12 August 1926, the KMT decided to launch a direct assault on Wu's stronghold of Wuchang, bypassing Sun's Nanchang. In this manner, they would follow the route taken by the Taiping Rebellion in the 19th century. In an address to his generals at the same conference, Chiang proclaimed:

"The importance of this fight is not only in that it will decide the fate of the warlords. But, whether or not the Chinese nation and race can restore their freedom and independence hangs in the balance. In other words, it is a struggle between the nation and the warlords, between the revolution and the anti-revolutionaries, between the Three People's Principles and imperialism. All are to be decided now in this time of battle … so as to restore independence and freedom to our Chinese race".

With the capture of the Yangtze port of Yuezhou on 22 August 1926, Hunan came under complete KMT control, paving the way for an advance to Wuchang along the route of the Beijing–Guangzhou railway. As Wu Peifu's forces retreated northward, they breached several Yangtze dikes, slowing the KMT push. By 28 August, the KMT, led by Li Zongren and his Guangxi NRA Seventh Army, had taken Xianning, about 75 kilometres (47 mi) south of Wuchang. Wu Peifu, who had returned south to mount a defence of Wuchang, gathered his forces at Heshengqiao Bridge. On 29 August, he launched a counterattack against KMT forces to the south, compromising his defensive line, and by noon the next day, his forces were in general retreat toward Wuchang. In this short period of time, Wu lost 8,000 troops. At least 5,000 of these were taken prisoner, along with their rifles, providing a boost to KMT forces. By 2 September, the NRA had nearly surrounded Wuchang. Whilst Wu and most of his army fled north to Henan province, his remaining troops in the walled city held out for over a month. His failure in the face of the NRA, however, left his hold on power and reputation broken. What remained of his army would disintegrate in the following months.