Mao relocated forces originally meant for the invasion of Taiwan to the northeast after the US 7th Fleet started patrolling the Taiwan Strait in June, making any invasion attempt impossible.When the Korean War started, Mao Zedong immediately dispatched several Army troops to the China - North Korea border, known as border guards, once they are in China's civil war, the fighting in the region over the forces, but also elite troops.
Stalin actually contacted Mao on October 5-7, warning of the possibility of US-Japan forces on the Chinese border. He also promised the USSR would "stand [behind] its ally."to my knowledge China sent troops to Korea, not after Mao Zedong met with Stalin.
One of the major goals of Kim Il Sung's invasion was to try and make his communist regime strong enough to break away from Chinese influence. He got plenty of armaments from Stalin, but refused Chinese help until the situation became hopeless in mid-September. He hated the idea that he would need to rely on his huge neighbour, why do you think there is so little official credit given to the hundreds of thousands of Chinese soldiers who died in North Korea? It's only mentioned when a Chinese leader visits every so often.With the North Korea military was defeated, Pyongyang was occupied, Kim Il-sung, fled into the mountains north of the border, Mao Zedong's request to send troops, after a night of consideration, Mao ordered border forces quietly went into North Korea border mountains area, and hiding there. While the UN troops in the northern mountain area combat with the residual North Korea troops , the Chinese army is also involved in a small-scale fighting, but the U.S. military not know.
the fighting subsided for a period of time that Mark arthur thought the North Korean army already have all escaped, but 300,000 chinese troops hiding in the north mountain area of North Korea, waiting for the opportunity, there is also commander Peng Dehuai plan military operations in this mountain area.
Mao hesitated when Stalin suddenly withdrew his promised "full support" in favour of limited support (ie. air support no closer than 100km from the front, which is basically no air support).When the UN forces large-scale entered to the north mountain area of North Korea, the Chinese army launched a military offensive to the UN troops, while Chinese army from China entered to North Korea, from northwest to southeast direction attack UN troops,with the hiding northern mountains of Chinese army operation, UN troops were surrounded and separated,
All of these occurre and Mao Zedong visited Soviet Union almost the same time, it is difficult to distinguish the right time,after Mao Zedong return to China the war officially announced.
Mao made his decision on Oct 13, and the first Chinese volunteers moved in between Oct. 16-19, delayed because of lack of forthcoming air support. The first contact between Chinese and US/UN forces was made on Oct. 25, the first Chinese POW captured on Oct. 26. Amazingly, Macarthur refused to heed the evidence that China was preparing to intervene and continued to drive towards the Yalu, which meant his forces would be far from their southern bases and stretched out in poor terrain. Major combat began on Nov. 26.