Wikipedia Deep Dive

Second United Front

11 min read

In December 1936, one of the most dramatic kidnappings in modern history changed the course of the Second World War before it had even begun. A Chinese warlord, fed up with his leader's priorities, abducted the head of the Chinese government and held him hostage until he agreed to stop fighting his domestic enemies and start fighting the Japanese. It worked.

This is the story of the Second United Front—an alliance born of desperation between two parties that despised each other, united only by their shared enemy. It would hold together just long enough to survive the Japanese invasion, then shatter into a civil war that reshaped Asia.

The Unlikely Partners

To understand why this alliance was so remarkable, you need to understand just how much the two parties hated each other.

The Kuomintang, or KMT, was the Nationalist Party that had governed China since 1928 under Chiang Kai-shek. They represented the established order—industrialists, landowners, urban elites. The Chinese Communist Party, or CCP, led by Mao Zedong, represented peasants and workers who wanted to overthrow that order entirely. These weren't just political opponents. They had been trying to exterminate each other for nearly a decade.

By 1935, the Communists were barely hanging on. Chiang's military campaigns had driven them into the remote northwest of China, where they clung to a small base area after their famous Long March—a grueling 6,000-mile retreat that killed most of their army. The Nationalists had the Communists surrounded and were preparing to finish them off.

But Japan had other plans.

The Japanese Shadow

Japan had been chipping away at Chinese territory since 1931, when they seized Manchuria—China's industrial heartland in the northeast. By the mid-1930s, Japanese forces were pressing deeper into northern China, and it was clear that a full-scale invasion was coming.

This created an excruciating dilemma for Chiang Kai-shek. He wanted to destroy the Communists first, then deal with Japan. His logic wasn't entirely crazy: why fight an external enemy when you have traitors within? But to ordinary Chinese people watching their country being carved up by foreign invaders, his priorities seemed backwards at best, treasonous at worst.

The pressure to form a united front against Japan came from an unexpected source: the Soviet Union. Joseph Stalin wanted China to tie down Japanese forces that might otherwise threaten Soviet territory. When Chiang approached Moscow for military aid in late 1935, the Soviets had a condition: make peace with the Communists.

Chiang was reluctant. He viewed the CCP as rebels and bandits. Negotiating with them would give them legitimacy they didn't deserve. But he needed Soviet weapons, so he cautiously reached out.

Secret Deals in the Northwest

While Chiang dragged his feet, the Communists were busy making their own deals.

The armies surrounding the Communist base weren't all loyal Nationalists. Many were regional forces commanded by warlords who had their own agendas. The Communists approached them quietly, playing on their frustration with Chiang's priorities.

Two generals proved receptive. Zhang Xueliang commanded the Northeastern Army—soldiers who had been driven from Manchuria by the Japanese invasion. They burned with desire to retake their homeland. Yang Hucheng led the Northwestern Army, local troops who resented being used as pawns in someone else's civil war. Both men were nominally loyal to Chiang, but both were increasingly disgusted by his obsession with the Communists while Japan swallowed Chinese territory.

In secret, they signed ceasefire agreements with the CCP.

This was remarkable. These generals were supposed to be besieging the Communists, not making deals with them. To hide their treachery, they staged fake battles. Their armies would advance, fire into the air, and report fierce combat to Nanjing. Meanwhile, the Communists grew stronger.

Another warlord, Yan Xishan, also signed a secret agreement with the CCP, though he kept more distance than Zhang or Yang. The northwest was becoming a web of secret alliances, all held together by one shared conviction: Japan was the real enemy.

Chiang Doubles Down

Chiang wasn't oblivious to these maneuverings, but he remained committed to crushing the Communists first. In late 1936, he thought he had them.

A Communist force had marched north trying to pick up weapons the Soviets had promised to drop in Mongolia. They got trapped on the wrong side of the Yellow River. Hui Muslim cavalry allied with the Nationalists cut them to pieces. It was a devastating blow to the Red Army.

Emboldened, Chiang began preparing another encirclement campaign. He sent his negotiators to meet with Communist representatives, but the terms he offered were humiliating—essentially demanding unconditional surrender. The Communist negotiator, Pan Hannian, called them "conditions for surrender" and refused.

In late November, Chiang ordered Zhang Xueliang's Northeastern Army to attack the Communist capital. Zhang was in an impossible position. His secret alliance meant he couldn't truly attack, but open defiance would expose him as a traitor. His solution was elegant: he sent his troops forward but held back most of his forces. The Communists, forewarned, ambushed the Nationalist units that did advance and nearly wiped out an entire regiment.

This disaster briefly softened Chiang's negotiating position. But it was too late. Zhang Xueliang had decided that persuasion wasn't working.

The Xi'an Incident

On December 12, 1936, Zhang Xueliang and Yang Hucheng made the most audacious gamble of their lives.

Chiang Kai-shek had come to Xi'an to personally oversee the campaign against the Communists. In the pre-dawn hours, Zhang's soldiers stormed Chiang's lodgings. The Generalissimo fled in his nightclothes, scrambling up a hillside in the freezing cold before being captured hiding in a crevice. China's leader had been kidnapped by his own generals.

The conspirators presented Chiang with demands: end the civil war, unite against Japan, reform the government. For two weeks, the fate of China hung in the balance. Hardliners in Nanjing wanted to bomb Xi'an. The Communists debated whether Chiang should be tried and executed.

In the end, everyone stepped back from the brink. The Communists, prodded by Stalin who wanted Chiang alive to fight Japan, sent Zhou Enlai to negotiate. Chiang agreed to the united front, though no formal document was ever signed—he refused to put his name to anything that looked like surrender to kidnappers. Zhang Xueliang, in a gesture of feudal loyalty that seems baffling today, personally escorted Chiang back to Nanjing, where he was promptly arrested. He would spend the next fifty-four years under house arrest.

But the united front was real. The Second United Front had begun.

The Terms of Alliance

The agreement that emerged was more practical than ideological. The Communist Red Army was reorganized into two units—the Eighth Route Army and the New Fourth Army—that were nominally placed under Nationalist command. The CCP agreed to accept Chiang's leadership, at least on paper. In return, they received some financial support from the Nationalist government and, crucially, were allowed to control two border regions where they could build their strength.

The Communists also won the right to publish newspapers in Nationalist areas. This might seem like a minor concession, but it allowed them to spread their message far beyond their base. The Xinhua Daily, still operating today as China's official news agency, got its start from this agreement.

Both sides knew exactly what they were getting. The Nationalists got Communist forces fighting Japan instead of them. The Communists got legitimacy, resources, and breathing room to rebuild after years of being hunted.

Neither side trusted the other for a moment.

Fighting Together, Sort Of

When full-scale war erupted in July 1937—Japanese troops poured into China after an incident at the Marco Polo Bridge near Beijing—the two parties did fight together. Initially.

Communist forces participated in the defense of Taiyuan in northern China. The high point of cooperation came during the Battle of Wuhan in 1938, when both armies defended the strategic city in central China. For a brief moment, it looked like the united front might actually work.

But the cooperation was always more theatrical than real. Communist forces answered to Communist commanders, not to the Nationalist chain of command. The CCP acted independently, focusing on goals that served their long-term interests rather than short-term military needs.

Mao Zedong was remarkably candid about his strategy. He argued that the Communists should trade space for time, letting the Nationalists bear the brunt of Japanese attacks while Communist forces built strength in the countryside. It was cold-blooded but rational. Why sacrifice your troops in conventional battles you couldn't win when you could expand your influence behind Japanese lines?

The Alliance Fractures

By late 1938, the fragile cooperation was breaking down.

Both parties were racing to control "Free China"—the areas not occupied by Japan or ruled by Japanese puppet governments. The Communists excelled at guerrilla warfare and rural organization. They moved into areas the Japanese nominally controlled and set up shadow governments, winning peasant support through land reform and anti-Japanese resistance. The Nationalists, watching Communist strength grow, grew alarmed.

Clashes began to occur. In June 1939, Communist forces under He Long attacked and destroyed a Nationalist militia brigade in Hebei province. Chiang noted the incident bitterly in his diary. The united front was becoming a competition to see who could expand faster while the Japanese occupied the cities.

The breaking point came in January 1941.

Chiang ordered the Communist New Fourth Army to evacuate Anhui and Jiangsu provinces in central China. The Communists partially complied, agreeing to move some troops north of the Yangtze River. But as the New Fourth Army moved through southern Anhui, Nationalist forces ambushed them.

What exactly happened remains disputed. Each side blamed the other for attacking first. What's clear is that thousands of Communist soldiers were killed or captured. The New Fourth Army's commander was imprisoned. The incident ended any pretense of cooperation between the two parties.

Civil War Behind Enemy Lines

After the New Fourth Army Incident, the war in China became three wars in one.

There was the war against Japan, which continued until 1945. But within the Japanese-occupied zones and the border regions, Nationalist and Communist forces also fought each other. The Communists gradually destroyed or absorbed most Nationalist guerrilla units operating behind enemy lines, either wiping them out or forcing them to defect to the Japanese puppet forces.

Meanwhile, Mao focused on building something that would outlast the war. Communist organizers spread through the countryside, setting up rural administrations, implementing land reform, organizing peasant associations. The Nationalists tried to contain this expansion through military blockades, but they were stretched thin fighting Japan.

By 1945, when Japan surrendered, the Communist position had been transformed. The party that had been on the verge of extinction in 1936 now controlled significant territory and commanded armies numbering in the hundreds of thousands.

The Aftermath

After the Japanese surrender, Chiang Kai-shek and Mao Zedong attempted peace talks. The United States, which had supported the Nationalists during the war, desperately tried to broker a coalition government. It failed.

By 1946, the two parties were locked in full civil war again. But this time, the balance had shifted. The Communists, with Soviet acquiescence, seized Japanese weapons stockpiled in Manchuria. The Nationalists, exhausted by eight years of fighting Japan, were riddled with corruption and had lost much of their popular support.

In October 1949, Mao Zedong stood at the Gate of Heavenly Peace in Beijing and proclaimed the People's Republic of China. Chiang Kai-shek fled to the island of Taiwan, where his Nationalist government continued to claim authority over all of China—a claim it maintained for decades.

The Legacy of an Improbable Alliance

The Second United Front is one of history's great examples of how enemies can cooperate when faced with a greater threat—and how such cooperation invariably contains the seeds of its own destruction.

Without the united front, the Communists might have been destroyed in 1936. The alliance gave them legitimacy, resources, and time to recover. It also gave them the opportunity to expand their influence across rural China while the Nationalists fought conventional battles against Japan.

The Nationalists, for their part, got Communist forces pointed at Japan instead of at them. But they were never able to fully control their allies, and they watched helplessly as Communist influence spread.

Perhaps the most remarkable figure in this story is Zhang Xueliang, the general who kidnapped Chiang Kai-shek and changed history. He expected to be executed for his treason. Instead, he spent fifty-four years under house arrest—first in mainland China, then in Taiwan after 1949. He was finally released in 1990, at age eighty-nine, and lived until 2001. He never expressed regret for what he had done.

The alliance he forced into existence lasted less than five years. But its consequences—the survival and eventual triumph of the Chinese Communist Party—shaped the entire twentieth century.