Amid heightening tensions, the Soviet Union and China began border talks. Although the Soviet Union had granted all of the territory of the Japanese puppet state of Manchukuo to the Chinese Communists in 1945, which decisively assisted them during the Chinese Civil War, the Chinese now indirectly demanded territorial concessions on the basis that the 19th-century treaties transferring ownership of the sparsely-populated Outer Manchuria, concluded by Qing dynasty China and the Russian Empire, were "Unequal Treaties" and amounted to the annexation of rightful Chinese territory. Moscow would not accept that interpretation, but by 1964 the two sides had reached a preliminary agreement on the eastern section of the border, including Zhenbao Island, which would be handed over to China.