IN THEIR RELATIONS with each other since the second Indochina War ended in 1975, both China and Vietnam have suffered complete foreign policy disasters. Neither country can gain from the most recent crisis in Sino-Vietnamese relations. Vietnam in particular, even with the most lavish self-interested Soviet aid, quite lacks the means to sustain a long-term enmity with China and to industrialize itself successfully at the same time. Since neither side can gain, it is obvious that each side has made catastrophic miscalculations about the other. But the mistakes and the passions which have inflamed Sino-Vietnamese relations have been generated more by the pressures of poverty and of national insecurity than by Chinese egocentricity or Vietnamese arrogance, whatever the claims of propagandists in both Peking and Hanoi. China's self-protective retaliatory invasion of the northern Vietnamese borderlands, which evidently involved tanks and hundreds of thousands of troops, and which lasted from the middle of February to the middle of March 1979, was only a most terrifying third act in a drama of tensions which had been in the making for years. As recently as November 1977, Le Duan, General Secretary of the Vietnamese Communist Party, could make a state visit to China in which he extravagantly informed Chinese and Vietnamese audiences that Sino-Vietnamese relations were developing increasingly well. He also thanked China for its chivalrous aid to Vietnam during the Indochina wars, declared that the most recent Chinese political occurrences had brought joy to the revolutionary peoples of all countries, and said that future Chinese support and aid would be an important source of encouragement during the rebuilding of Vietnam.' Behind the scenes his language must have been different. For