On October 1, 1950, Beijing's Tiananmen Square was filled with a large crowd celebrating the first anniversary of the founding of the People's Republic of China. But the joyous occasion belied a threat the fledgling republic was facing to its very existence. A war that could have far-reaching repercussions for China had been raging on the neighboring Korean Peninsula for over three months. 

This day was significant because Mao Zedong, who presided over the nascent republic for exactly a year, received both a handwritten request for military assistance from Kim II Sung, leader of the Democratic People's Republic of Korea, and a Soviet telegram calling for China to send troops into Korea.

At the time, China was facing threats on multiple fronts, and the United States, wielding three daggers aimed at China, was the one responsible for posing these threats. The U.S. intervention in the Korean War was believed to be aimed at China's head, the U.S. deployment of its 7th fleet in the Taiwan Straits at China's waist and the U.S. support for France's colonial war in Vietnam at China's feet.

But China's protests against such aggression had fallen on deaf ears in the international community. On the Korean front, U.S. military encroachment was certainly not slowed.

Emergency meetings were held in the late evening of October 1. Hours later, Mao and other CPC leaders reached a preliminary decision to dispatch forces into Korea. But a host of domestic concerns were keeping that decision from being finalized.

Against the backdrop of a China that did not want to enter another war, U.S. air forces' rampant violation of Chinese air space, reports of U.S. troops crossing the 38th Parallel and the conviction that Americans would cross the Yalu River into China if they captured Korea in its entirety had all contributed to the motivating forces behind China's final decision on military deployment into Korea.

The determination to resist U.S. aggression was also reinforced as China was resolved to shake off the relentless humiliations it had suffered at the hands of Western powers. The call to "resist America, aid Korea and protect the motherland" began to reverberate across China, galvanizing people's fighting spirit and eclipsing concerns for U.S. military's clear superiority.

Though the sharply asymmetrical nature of the incoming warfare did not stop soldiers from pressing on, a last-minute Soviet backdown from its promise to provide air support caused hesitancy among the Chinese leadership. Mao needed to think again. But war never waits until one is ready.

A nation that had only just emerged from one war was under pressure to enter another. The fate of the Chinese nation was hanging in the balance. The decision was a very difficult one, and once taken, it would be irrevocable.

"Even if we cannot beat America, they will be beholden to us. We can fight them again if we so wish," Mao said before finally settling on a decision.

At 6 p.m. on October 19, four army corps and three artillery divisions of the Chinese People's Volunteers army crossed the Yalu River.