During the Cold War, The West was concerned with the spread of communism however the communist nations had their own in-fighting. China and the Soviet Union had a bitter relationship after the death of Joseph Stalin. After American forces left Vietnam, the new government sided more with the Soviets than China. This with other reasons led China to invade Vietnam which caused the Sino-Vietnamese War. It lasted less than a month in a practical stalemate though both sides claimed victory over the other.