The Second United Front () was the alliance between the ruling Kuomintang (KMT) and the Chinese Communist Party (CCP) to resist the Japanese invasion of China during the Second Sino-Japanese War, which suspended the Chinese Civil War from 1937 to 1945.
Background
In 1927 the Chinese Communists retaliated against Kuomintang following a betrayal of its members in Shanghai by National Revolutionary Army commander Chiang Kai-shek, which marked the end of the KMT's four-year alliance with the Soviet Union and its cooperation with the CCP during the Northern Expedition (aka First United Front) to defeat warlords and unify China.
In 1931 the Japanese launched its invasion and subsequent occupation of Manchuria. Chiang Kai-shek, who de facto led the central government of China, decided that China must avoid all-out war with Japan due to domestic turmoil and inadequate preparation. Therefore, he "pursued a strategy of appeasing Japan while struggling for real national unity and over time sufficient strength to confront the Imperial army. This appeasement policy lasted for another six years". Even though his campaigns against the Communists resulted in their retreat and a 90% reduction in their fighting strength, he was unable to eliminate their forces entirely, and his policy of "internal pacification before external resistance" (:) was very unpopular with the Chinese populace, which caused widespread resentment and demonstration against the ruling KMT leadership and its regional warlord allies.
Xi'an Incident
In 1936, Chiang Kai-shek assigned "The Young Marshal" Zhang Xueliang, leader of Northeastern Army, the duty of suppressing the Red Army of the CCP. Battles with the Red Army resulted in great casualties for Zhang's forces, but Chiang Kai-shek did not provide any support to his troops.
On 12 December 1936, a deeply disgruntled Zhang Xueliang kidnapped Chiang Kai-shek in Xi'an to force an end to the conflict between KMT and CCP. To secure the release of Chiang, the KMT was forced to agree to a temporary end to the Chinese Civil War and the forming of a united front between the CCP and KMT against Japan on 24 December 1936. However, by the time Chiang arrived in Xi'an on 4 December 1936, negotiations for a united front had been in the works for two years.
The China Democratic League, an umbrella organization for three political parties and three political pressure groups, also agreed to take part in the united front formed by KMT and the CCP.
Cooperation during the War of Resistance
As a result of the truce between KMT and CCP, the Red Army was reorganized into the New Fourth Army and the 8th Route Army, which were placed under the command of the National Revolutionary Army. The CCP agreed to accept the leadership of Chiang Kai-shek, and began to receive some financial support from the central government run by KMT. In agreement with KMT Shaan-Gan-Ning Border Region and Jin-Cha-Ji Border Region were created. They were controlled by the CCP.
After the commencement of full-scale war between China and Japan, the Communists forces fought in alliance with the KMT forces during the Battle of Taiyuan, and the high point of their cooperation came in 1938 during the Battle of Wuhan.
However, the Communists submission to the chain of command of the National Revolutionary Army was in name only. The Communists acted independently and hardly ever engaged the Japanese in conventional battles. The level of actual coordination between the CCP and KMT during the Second Sino-Japanese War was minimal.
Breakdown and aftermath
In the midst of the Second United Front, the Communists and the Kuomintang were still vying for territorial advantage in "Free China" (i.e. those areas not occupied by the Japanese or ruled by puppet governments). The uneasy alliance began to break down by late 1938 as a result of the Communists' efforts to aggressively expand their military strength through absorbing Chinese guerrilla forces behind enemy lines. For Chinese militia who refused to switch their allegiance, the CCP would call them "collaborators" and then attack to eliminate their forces. For example, the Red Army led by He Long attacked and wiped out a brigade of Chinese militia led by Zhang Yin-wu in Hebei in June, 1939.