The temporary alliance between the Kuomintang (KMT) and the Communist Party of China (CPC) in 1937 is one of the most significant turning points in modern Chinese history. Known as the Second United Front, this cooperation was formed during a time of extreme national crisis when China faced a full-scale invasion by Imperial Japan. When examining why the Kuomintang and the CPC united in 1937, it becomes clear that their decision was driven less by mutual trust and more by urgent necessity. Both parties recognized that internal conflict had to be set aside in order to resist a powerful external enemy that threatened the survival of China itself.
Historical Background of KMT and CPC Relations
Early Cooperation and Breakdown
The Kuomintang and the Communist Party were originally allies during the First United Front in the 1920s. At that time, both groups worked together to unify China and end the rule of warlords. However, this cooperation collapsed in 1927 when Chiang Kai-shek, leader of the Kuomintang, launched a violent purge against communists in what became known as the Shanghai Massacre.
After this event, China entered a long period of civil war between the KMT and CPC. The two sides became bitter enemies, fighting for political control, military dominance, and ideological influence over the country.
The Rise of Internal Conflict
Throughout the early 1930s, the Chinese Civil War intensified. The Kuomintang controlled most major cities and official government structures, while the CPC retreated to rural areas and built revolutionary bases.
This internal struggle weakened China as a whole, making it vulnerable to foreign aggression, especially from Japan, which had been expanding its influence in Manchuria and other parts of northeastern China.
The Japanese Invasion and National Crisis
Manchuria and Early Aggression
In 1931, Japan invaded Manchuria and established the puppet state of Manchukuo. This marked the beginning of a broader Japanese expansion into Chinese territory. The Kuomintang government responded weakly at first, focusing more on internal communist suppression than external threats.
This decision was controversial and created widespread criticism among Chinese citizens who believed that national defense should be the priority.
Escalation in 1937
The situation dramatically worsened in 1937 with the Marco Polo Bridge Incident, which triggered a full-scale war between China and Japan. Japanese forces launched a massive invasion, attacking major cities and military positions across China.
This event marked the beginning of the Second Sino-Japanese War, which would later become part of World War II.
Why the Kuomintang and CPC United in 1937
Common Enemy Japan
The primary reason for the temporary alliance between the Kuomintang and the Communist Party was the shared threat of Japanese invasion. Both sides recognized that continuing their civil war would weaken China and make resistance against Japan impossible.
Despite deep ideological differences, the urgency of national survival forced both parties to reconsider their priorities.
Pressure from the Chinese People
Public opinion in China strongly favored unity against Japan. Students, intellectuals, and ordinary citizens demanded that the KMT and CPC stop fighting each other and focus on resisting foreign invasion.
This growing pressure made it politically difficult for either side to continue internal conflict without appearing unpatriotic.
The Xi’an Incident
A key event that led to the formation of the Second United Front was the Xi’an Incident in December 1936. During this incident, Chiang Kai-shek was detained by his own generals, Zhang Xueliang and Yang Hucheng, who demanded that he stop the civil war and focus on resisting Japan.
Under pressure, Chiang Kai-shek agreed to negotiate with the Communist Party, leading to a temporary alliance in 1937.
The Formation of the Second United Front
Official Agreement
In 1937, the Kuomintang and the CPC officially agreed to form the Second United Front. This alliance was intended to unify Chinese military forces against Japan while maintaining separate political identities.
The agreement allowed the CPC to retain some autonomy while nominally recognizing the authority of the KMT-led national government.
Military Cooperation
Under the alliance, Communist forces were incorporated into the National Revolutionary Army as part of the Eighth Route Army and New Fourth Army. These units were tasked with guerrilla warfare and resistance operations against Japanese forces.
The Kuomintang continued to control major conventional military operations, especially in urban and strategic areas.
Goals of Each Side in the Alliance
Kuomintang Objectives
The Kuomintang viewed the alliance as a way to unify China temporarily under its leadership while focusing on defeating Japan. Chiang Kai-shek believed that cooperation with the CPC was necessary but expected to resume civil conflict after the war.
The KMT aimed to maintain political dominance and strengthen its legitimacy as the ruling government of China.
Communist Party Objectives
The CPC saw the alliance as an opportunity to survive and expand its influence. By participating in the resistance against Japan, the Communists gained popular support, military experience, and access to new territories.
They also used guerrilla warfare to build strong rural bases and increase their political influence among peasants.
Challenges in the Alliance
Lack of Trust
Despite the agreement, deep mistrust remained between the Kuomintang and the CPC. Both sides suspected the other of using the alliance for strategic advantage rather than genuine cooperation.
Incidents of conflict and sabotage occasionally occurred even during the united front period.
Different Military Strategies
The Kuomintang preferred conventional warfare and defending major cities, while the Communist Party focused on guerrilla tactics in rural areas. These differences sometimes created tension in coordination efforts against Japanese forces.
Impact of the Second United Front
Resistance Against Japan
The alliance allowed China to present a more unified resistance against Japanese invasion. Although coordination was imperfect, both the KMT and CPC contributed to the broader war effort.
Guerrilla warfare, large-scale battles, and civilian resistance all played roles in slowing Japanese advances.
Strengthening of the Communist Party
One of the unintended consequences of the alliance was the strengthening of the Communist Party. By operating in rural areas and engaging in resistance efforts, the CPC gained significant support from peasants and expanded its military capabilities.
This growth would later play a crucial role in the outcome of the Chinese Civil War.
End of the Alliance
Collapse After World War II
The Second United Front effectively ended after Japan’s defeat in 1945. Once the common enemy was removed, tensions between the Kuomintang and CPC quickly resurfaced.
The civil war resumed shortly after, eventually leading to the Communist victory in 1949 and the establishment of the People’s Republic of China.
Return to Civil War
Despite temporary cooperation, the underlying ideological conflict between nationalism and communism remained unresolved. The alliance was never intended to be permanent and collapsed once external pressure disappeared.
The Kuomintang and the Communist Party of China united in 1937 primarily because of the urgent threat posed by the Japanese invasion. Facing a powerful external enemy, both sides recognized that internal conflict had to be temporarily set aside in order to defend the nation. The Xi’an Incident, public pressure, and the escalation of the Second Sino-Japanese War all contributed to the formation of the Second United Front.
Although the alliance was fragile and filled with mistrust, it played a crucial role in China’s resistance during World War II. At the same time, it reshaped the balance of power between the two parties, ultimately influencing the outcome of the Chinese Civil War that followed. The unity of 1937 remains a key example of how external threats can temporarily bring together deeply divided political rivals.