Huanggutun incident in the context of "Northeastern Army"

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 Fengtian Government (Chinese: 奉系军阀; pinyin: Fèngxì Jūnfá; Wade–Giles: Feng-hsi Chün-fa) was the faction that supported warlord Zhang Zuolin during China's Warlord Era. It took its name from Fengtian Province, which served as its original base of support. However, the clique quickly came to control all of the Three Northeastern Provinces. The clique received support from Japan in exchange for protecting Japanese military and economic interests in Manchuria. The Fengtian Army frequently intervened in many of the conflicts of the Warlord Era.

Following the Zhili–Anhui War of 1920 and 1921, the Fengtian and Zhili cliques exercised joint control of Beijing and the Beiyang Government. Tensions soon began building between the two, resulting in clashes for control of Beijing known as the First Zhili–Fengtian War (1922). The Second (1924) Zhili–Fengtian War started later over the Zhili invasion of the remnants of the Anhui clique, which had become allies of the Fengtian Clique, which resulted in a Fengtian victory, with the Zhili clique retreating as far south as Henan. The power of the Fengtian Clique began to decrease in the midst of the Kuomintang's Northern Expedition. In 1928, while he was retreating North, Zhang Zuolin's Japanese sponsors blew up his train, killing him. After Zhang's assassination, his son, Zhang Xueliang, took over the leadership of the clique. He preferred to work with the Kuomintang rather than the Japanese and symbolically pledged allegiance to the Nationalist Government in Nanjing. In practice, the Fengtian clique continued to independently govern Manchuria until the Japanese invasion in 1931.

Zhang Zuolin (March 19, 1875 – June 4, 1928) was a Chinese warlord who ruled Manchuria from 1916 until his assassination in 1928, he led the Fengtian clique, one of the most powerful factions during the Warlord Era. In 1927, he became the leader of the Beiyang government and was declared Generalissimo of the Republic of China.

Born to a poor peasant's family in Manchuria, Zhang became a prominent mounted bandit in the region in the 1890s. After the Boxer Rebellion, his troops became a regiment of the Qing dynasty's army, and during the Russo-Japanese War, they were hired by the Japanese Army as mercenaries. During the 1911 Revolution, Zhang initially fought against the revolutionaries, and after the foundation of the Republic of China supported the Beiyang government. Zhang founded the Fengtian clique and gradually expanded his Northeastern Army, which established his supremacy over the three northeastern provinces (Fengtian, Jilin and Heilongjiang).

Zhang Xueliang (Chinese: 張學良; June 3, 1901 – October 15, 2001), also commonly known by his nickname "the Young Marshal", was a Chinese general who in 1928 succeeded his father Zhang Zuolin as the commander of the Northeastern Army. He is best known for his role in the Xi'an Incident in 1936, in which he arrested Chiang Kai-shek and forced him to form a Second United Front with the Chinese Communist Party against the Japanese.

In 1928, Zhang, at the time a general in the Northeastern Army, became the commander of the army and leader of the Fengtian clique upon his father's assassination. A reformer sympathetic to nationalist ideas, he completed the official reunification of China by pledging loyalty to the Nationalist government, and used his powerful base to wield significant influence in the politics of the Nanjing decade. Zhang followed Chiang's policy of nonresistance to the Japanese invasions of Manchuria in 1931 and Rehe in 1933, after which he was forced to resign as head of the Northeastern Army.

Baron Tanaka Giichi (Japanese: 田中 義一; IPA: [ta̠na̠ka̠ ɡʲiːt͡ɕi]; 22 June 1864 – 29 September 1929) was a Japanese general and politician who served as Prime Minister of Japan from 1927 to 1929.

Born to a samurai family in the Chōshū Domain, Tanaka became an officer in the Imperial Japanese Army and rose through the ranks. He served as Minister of the Army under Prime Ministers Hara Takashi and Yamamoto Gonnohyōe. After retiring from active duty he accepted the presidency of the Rikken Seiyūkai, a major conservative party. Following the resignation of the Wakatsuki Cabinet in 1927, Tanaka was appointed Prime Minister. In foreign affairs, he pursued a hawkish policy; in domestic affairs, he sought to suppress communist and socialist movements. Criticised for his handling of the unauthorised assassination of Zhang Zuolin by a Kwangtung Army officer, he resigned in 1929 and died soon afterwards.