The Yalta Agreement, or the Tripartite Agreement on Japan, was secretly signed by Premier Stalin of the Soviet Union, President Roosevelt of the United States and Prime Minister Churchill of Great Britain at Yalta (Crimea, USSR) on February 11, 1945. The main element of the agreement was that within two or three months after the European war was over the Soviet Union would intervene against Japan. In return for this, the other two parties promised to maintain the status quo in Outer Mongolia, to return to the Soviet Union the territories lost in the Russo-Japanese war of 1905, as well as the Kuril Islands, and to restore Soviet rights and interests in China's Northeast. The Soviet Union expressed its willingness to sign a pact of friendship and alliance with China's Kuomintang government.

105 Immediately after the outbreak of a civil war in Korea on June 25, 1950, the United States, under the banner of the United Nations, sent troops to intervene and at the same time sent its Seventh Fleet into the Taiwan Straits. On September 15, U.S. troops landed at Inchon on the west coast of Korea, then crossed the 38th Parallel, the provisional line of demarcation between North and South Korea, and pushed north en masse, bombing and strafing the frontier cities and villages of Northeast China and posing a serious threat to China's security. To resist the United States, aid Korea and safeguard the homeland, the Chinese people organized the Chinese People's Volunteers. On October 25 the Volunteers arrived at the Korean battlefield and fought shoulder to shoulder with the Korean People's Army. Under the heavy blows of the Chinese and Korean people's armies, the U.S. troops suffered one defeat after another and on July 27, 1953, had to sign an armistice agreement.