1979 Sino-Vietnamese War

I am so glad I started subscribing to the print issue of The Economist again. I get it in the mail on Saturdays and I read it cover-to-cover (for the most part). I really enjoy the obscure historical trivia the stories contain. Here's one: The 1979 invasion of Vietnam. China and the USSR were enemies. China's proxy in Cambodia (Pol Pot) was just toppled by Vietnam (supported by the Soviet Union). So China briefly attacked Vietnam's land border as punishment.