Despite the COVID-19 pandemic and perhaps in some ways because of it, conflicts of interest between the United States and China seem only likely to increase in the coming years. As conflicts of interest between these two states increase, one central question for scholars and policy-makers is the probability of different causal mechanisms whereby a conflict of interest generates a crisis and the crisis becomes a limited, conventional or even nuclear war. Another important and closely related question is which allies Washington and Beijing can count on to do what as these conflicts of interest grow. Unlike China, the United States has alliances that span the world, with formal defence commitments throughout Europe and Asia. If alliances do more than aggregate but substantially multiply U.S. power, exactly what do they bring to the table?