The Sino-Vietnamese War took place in early 1979 between China and Vietnam. The war was sparked by China's response to Vietnam's actions against the Khmer Rouge in 1978, which had ended the rule of the Chinese-backed Khmer Rouge. Both sides claimed victory in the final conflict of the Indochina Wars. During the war, Chinese forces invaded northern Vietnam and captured several cities near the border. On March 6, 1979, China declared that it had achieved its objective and its troops then withdrew from Vietnam. However, Vietnam continued to maintain troops in Cambodia until 1989, thus China's goal of dissuading Vietnam from involvement in Cambodia was not fully achieved. Following the collapse of the Soviet Union in 1991, the Sino-Vietnamese border was settled. Although China was unable to stop Vietnam from ousting Pol Pot from Cambodia, it demonstrated that the Soviet Union, its Cold War communist adversary, was unable to protect its Vietnamese ally.