On December 16, 1949, Mao left for a visit to Moscow, accompanied by numerous experts. He was warmly welcomed and attended the celebrities for the 70th birthday of Joseph Stalin, but was then deliberately left alone in a datcha for many weeks. Perhaps Stalin humiliated the newcomer in the east in order to demonstrate who the real leader of the communist hemisphere was. Negotiations finally began in January, and the CPC achieved on February 14, 1951 the Treaty of Friendship, Alliance and Mutual Assistance (Zhong-Su youhao tongmeng huzhu tiaoyue 中苏友好同盟互助条约, Договор о дружбе, союзе и взаимной помощи) with the Soviet Union.
For Stalin, the PRC played an important role in the containment of U.S. imperialism in East Asia, and therefore welcomed a new member in the socialist camp to bring forward the cause of the world revolution. For Mao Zedong, international recognition was an important point, but also the financial, military and technical aid the SU provided to him. This matter was so important that he accepted that the Soviet Union still exerted considerable power in East Asia, still dominated Xinjiang (also because of the cross-border distribution of some peoples like the Kazakhs or Tadjiks), controlled Outer Mongolia (the People's Republic of Mongolia), and possessed the China Eastern or Changchun Railway (Dongqing tielu 东清铁路, Китайско-Восточная железная дорога) and ports (Port Arthur; today's Lüshunkou 旅顺口, Liaoning, close to Dairen [Japanese name]/Dalian大连, old name Lüda 旅大) on Chinese soil, and did not claim compensation for Russia's plundering of the Manchurian industry after the Anti-Japanese War.
The Treaty, valid for thirty years, promised mutual military aid if either party was attacked by Japan or one of its allies. Reciprocal consultations were to be held on all international problems of common interest. A further document was an agreement on the handover of the Changchun Railway in 1952 at the latest, and Soviet troops would withdraw from Port Arthur. In a third document, the SU granted China a loan of $300 million, repayable until 1963 at an interest rate of 1 per cent. Further agreements concerned the creation of mixed Sino-Soviet oil and metal companies in Xinjiang, as well as that of an aviation company.
After the conclusion of the Sino-Soviet Treaty in early 1950, a wave of interest into Russia, Russian language, and Russian literature and cinema, went through China.