The 70th year of the IAU has been marked not only by the Covid-19 pandemic but by the geopolitical tension between the United States and China. After almost four decades of cooperation, which began in shared opposition to Soviet Russia and a shared interest in China’s modernisation, the leaders of each country have become strident critics of the other. The escalating war of words has led to disruptions in trade, communications and visas and now threatens the vast and fruitful cooperation between universities and researchers. Much is at stake. Many US universities are in China, such as Stanford with its state-of-the-art centre at Peking University and NYU with a branch campus in Shanghai. Chinese universities benefit from visits in both directions, from bench-marking using American partner templates and from the return of US-trained doctoral graduates. US-China links in science are focused on crucial areas like biomedicine and epidemiology, planetary science and ecology, engineering, materials, energy, cybernetics.