Meaning: The quote "The unthinkable occurred: two communist countries went to war with each other." by Neil Sheehan, a journalist, refers to the little-known but significant conflict between China and Vietnam in 1979. This event was indeed unthinkable to many at the time, as it defied the assumption that communist countries would always stand united against their common enemies. The war between China and Vietnam was a complex and significant event in the context of the Cold War and the dynamics of international communism.

The conflict between China and Vietnam had its roots in the broader geopolitical landscape of the Cold War. Both countries were communist states, but their relationship was strained due to ideological and territorial disputes. The Chinese Communist Party, under the leadership of Mao Zedong, had initially supported the Vietnamese communists in their struggle against French colonialism and later against American intervention in the Vietnam War. However, as the Vietnam War came to an end with the fall of Saigon in 1975, tensions between China and Vietnam began to escalate.

One of the primary reasons for the conflict was the strategic and territorial rivalry between China and Vietnam. The border disputes between the two countries, particularly concerning the Paracel and Spratly Islands in the South China Sea, had been a longstanding source of tension. Additionally, Vietnam's close alignment with the Soviet Union, China's rival in the communist world, further strained relations between the two countries.

The immediate trigger for the war was Vietnam's invasion of Cambodia in late 1978. The Khmer Rouge regime in Cambodia, led by Pol Pot, had committed atrocities against its own people, leading to a humanitarian crisis. Vietnam, viewing the Khmer Rouge as a threat to its security, intervened militarily and overthrew the regime. This action was met with strong condemnation from China, which had been a key supporter of the Khmer Rouge and saw Vietnam's intervention as a threat to its influence in the region.

In response to Vietnam's intervention in Cambodia, China launched a full-scale invasion of northern Vietnam in February 1979. The Chinese forces advanced into Vietnamese territory, engaging in fierce battles with the Vietnamese army. However, the war proved to be a costly and ultimately unsuccessful endeavor for China. Despite initial gains, the Chinese forces faced strong resistance from the Vietnamese, and after several weeks of fighting, they withdrew from Vietnam.

The war had significant implications for the broader Cold War dynamics and the global communist movement. It shattered the perception of a monolithic communist bloc and highlighted the deep divisions and rivalries within the communist world. The conflict also had a profound impact on the regional balance of power in Southeast Asia, leading to a realignment of alliances and a shift in the geopolitical landscape of the region.

In the aftermath of the war, the relationship between China and Vietnam remained tense, with sporadic border clashes continuing in the following years. It was not until the 1990s that the two countries began to normalize their relations, as both underwent significant changes in their domestic and foreign policies.

In conclusion, Neil Sheehan's quote captures the surprising and momentous nature of the war between China and Vietnam. The conflict was a stark reminder of the complexities and contradictions within the communist world, and it had far-reaching implications for the Cold War and the dynamics of international relations in the Asia-Pacific region.