Northeast Flag Replacement in the context of "Kuomintang"

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.

The Northeastern Army, also known as the Fengtian Army (see terminology), was a Chinese army that existed from 1911 to 1937. General Zhang Zuolin developed it as an independent fighting force during the Warlord Era. He used the army to control Northeastern China (Manchuria) and intervene in national politics. During the mid-1920s the Northeastern Army was the dominant military force in China, but in 1928 it was defeated by the Kuomintang's National Revolutionary Army (NRA) during the Northern Expedition. At the end of that campaign, Zhang Zuolin was assassinated and succeeded by his son Zhang Xueliang. When Xueliang subsequently pledged loyalty to the Kuomintang, the Northeastern Army became part of the NRA and was officially rechristened the "Northeastern Border Defense Force".

Despite being formally part of the NRA, the Northeastern Army remained de facto Zhang Xueliang's personal army. Zhang used the army to exercise considerable political influence during the tumultuous early years of the Nanjing Decade. The Japanese invaded Manchuria in 1931 and forced the Northeastern Army to retreat into northern China. After the army was unable to prevent further Japanese annexations of Chinese territory, Zhang was temporarily removed from command. In 1935, the army was reassigned to the Gansu-Ningxia border area in an attempt to encircle the Chinese Communist Party (CCP)'s base there. Both Zhang and his soldiers resented fighting fellow Chinese while Manchuria was under occupation. They negotiated a covert ceasefire with the CCP and hoped to convince Chiang Kai-shek to endorse a united front against Japan. After Chiang refused, the Northeastern Army kidnapped him and forced him to negotiate with the Communists. Although Chiang eventually agreed to end the civil war and work with the Communists against Japan, Zhang was placed under house arrest and the Northeastern Army was divided and reassigned to other commands.

The Warlord Era was a historical period of the Republic of China that began from 1916 and lasted until the mid-1930s, during which the country was divided and ruled by various military cliques following the death of Yuan Shikai in 1916. Communist revolution broke out in the later part of the warlord period, beginning the Chinese Civil War. The era nominally ended in 1928 at the conclusion of the Northern Expedition with the Northeast Flag Replacement, beginning the "Nanjing decade". However, "residual warlords" continued to exist into the 1930s under de jure Kuomintang rule, and remained until the Communist victory in the Chinese Civil War in 1949.

The warlords and military cliques of the Warlord Era are generally divided into the Northern factions and the Southern factions. The following is a list of cliques within each faction, and the dominant warlords within that clique.