when did relations between china and the soviet union begin to improve
Sino-Soviet relations Since the Sino-Soviet Treaty of Friendship resulted in the Soviet Union losing its naval bases in Port Arthur and Dalian, the issue that Stalin had to face was to find a new ice-free port as a Soviet naval base. This issue motivated Stalin's support for allowing Kim Il-Sung to launch the Korean War.[4] However, both Kim Il-Sung and Stalin did not consider that the United States would intervene into that war immediately, if at all. Kim Il-Sung could not sustain the attack against the US Army. When Kim Il-Sung required military assistance from the Soviet Union and China, Mao agreed to send Chinese troops, but asked the Soviet Air Force to provide air cover. As the two leaders distrusted each other, Stalin agreed with sending Chinese troops to Korea, but refused to provide air cover.[5] Since without the air cover from the Soviet Union, Mao once considered that China did not send troops into Korea, and Stalin at one time decided to give up the Korea Peninsula.[5] After much cogitation, Mao solely sent Chinese troops into Korea on 19 October 1950 under an extremely hard Chinese economic and military situation. This activity ultimately changed the Sino-Soviet relationship. After 12 days of Chinese troops entering the war, Stalin allowed the Soviet Air Force to provide air cover, and supported more aid to China.[5] Mao sending Chinese troops to take part in the Korean War was followed by large-scale economic and military cooperation between China and the Soviet Union, and the friendly relationship of the two countries changed from titular to virtual. In one less known example of the Sino-Soviet military cooperation, in Aprilâ€“June 1952 a group of Soviet Tupolev Tu-4 aircraft were based in Beijing to perform reconnaissance missions on American fusion bomb tests in the Pacific.[6]